Skyview Wines & Liquors, hidden away in a corner of the drab little Food Emporium shopping center in a sleepy northern extremity of the Bronx, is easy to overlook. But to catch the new wave of kosher wine, you need to know about Skyview. While its selection of standard wines is humdrum, this unsleek shop has become the primary source for fine wines that also happen to be kosher, a category that is rapidly growing. Skyview’s all-kosher aisles, representing half the shop’s inventory, are lined with more than 450 different wines ranging from Amiad Merlot to Zakon Chardonnay. In all, 11 countries are represented.

As Passover approaches, the pace is frenetic at Skyview. Modest numbers of customers were milling about when I visited the shop last Thursday, but they were the iceberg’s tip. Telephone and Internet orders, along with sales generated by synagogue wine tastings, account for much of the volume, according to owner Jeff Saunders. So many cases of wine awaiting delivery were stacked around the shop’s entrance that I had to ease my way in. Sixteen cases, I noted, were headed for a residential address in Los Angeles.

“Why would an Angeleno buy from the Bronx?” I asked the 49-year-old Mr. Saunders, who is at the gym most mornings at 6 a.m. and has the kind of sculpted figure that the governor of California wishes he still had.

“Maybe because the prices are better here,” he answered. Mr. Saunders demurred at estimating Skyview’s total sales, but he said that in this holiday season Skyview is selling 300 to 400 cases of kosher wine every day. Another volume spike will occur in the fall, as the Jewish High Holidays approach.

For certain boutique kosher labels, Skyview is the only source with deep inventory. The superb burgundian-style wines of Domaine du Castel, a winery nestled in the hills near Jerusalem, for example, are hard to locate elsewhere in the city. And no wonder. I counted more than 30 cases of Castel wines stacked in a vacant commercial building adjacent to Skyview. “I bought all I could get,” Mr. Saunders said. “By the time Passover comes, every case that you see will be gone.”

Jewish history is long, but the era of kosher wines that can compete with the best secular wines is barely upon us. For the faithful, the first purpose of wine is to be sipped from the kiddish cup after a blessing is recited to welcome the Sabbath. Swirling, sniffing, and sipping a cabernet sauvignon aged in oak was never part of the game. But it is now, and the new period of the kosher wine geek can be dated to the mid-1980s when Yarden – a new Israeli winery carved out of former apple orchards on the Golan Heights – first released its elegant and age-worthy wines made from classic French grapes. The first high quality kosher wine from France itself, in Mr. Saunders’s judgment, was the Barons de Rothschild Haut-Medoc, vintage 1986.

The kosher wine arena is now crowded with an international array of competitors. At least a dozen Israeli wineries now compete with Yarden, not least the formerly sleepy Carmel – the first and largest Israeli winery – which has introduced a line of super-premium single-vineyard wines. A handful of all-kosher wineries, including Herzog, Hagafen, and Weinstock, have taken root in California. And numerous conventional wineries, ranging from Chateau Giscours in Margaux to Teal Lake in Australia, now allow crews of observant Jews to make kosher lots of their wines. The winemaker himself, however, need not be observant so long as he does not touch the wine. Joe Hurliman, winemaker at the fully kosher Herzog Wine Cellars in Oxnard, Calif., for example, has become an expert in the myriad fine points of kosher wine requirements, but he is not Jewish.

So what makes a wine kosher? No regulations come from the Bible, which is precise on what makes food kosher but silent on wine. By custom, wine is kosher if it is vinified in specially maintained containers, using only permitted yeasts and fining agents, and is handled only by observant Jews until it reaches the customer. It must also be served by observant Jews, unless it is mevushal (“boiled” in Hebrew),a flash-heating process after which the wine can be served by anyone. Many wineries reject the mevushal process, fearing that it will detract from the taste and aging ability of their wines. About half of Skyview’s kosher inventory is also mevushal.

It isn’t always easy being a purveyor of kosher wines. A mini-crisis loomed, for example, during my visit to Skyview, when shop manager Tony Potenza opened 10 Passover-certified wines for an in-store tasting. The wines were to be poured by a distributor’s representative. But upon his arrival, the representative refused to pour wines not opened by an observant Jew. Mr. Potenza is not Jewish, but even Mr. Saunders, who is, would not have been allowed to open the wines. “I am a Jew who lays tefillin (prayer phylactories) every morning,” he explained, “but I’m not Sabbath observant.” Mr. Saunders worked out a solution: Customers would pour their own wines until the original bottles were emptied. Replenishment bottles would be opened by the representative, who would then take over the pouring.

Mr. Saunders, whose father was a liquor store broker, bought Skyview in 1984 from two older men who were retiring. The pair agreed to stay on premises as advisers for a few weeks. Then, as now, it was the Passover season, and kosher wine sales were brisk. Very brisk. “After three hours, I told these guys they could go home,” Mr. Saunders said. “I knew kosher wine was going to be my future.”

In that pre-Internet era, Mr. Saunders built Skyview’s reputation as a kosher kingdom mainly by hosting tasting events at synagogues. He also puts his kosher inventory on sale as the Jewish holidays approach. Passover brings the year’s lowest prices. Comparing prices on half a dozen widely available kosher wines, I found that Skyview undercut several Manhattan stores on all of them. Yarden Cabernet Sauvignon 2000, for example, is $21.99 at Astor Wines and $17.95 at Skyview, while the kosher bottling of Nicholas Feuillatte Brut Champagne is $39.95 at Sherry-Lehmann and $34.95 at Skyview.

“I discount steeply at Passover,” Mr. Saunders said, “because it gets me a customer for life.”

Skyview Wine & Liquors, 5681 Riverdale Ave., Bronx, 718-601-8222, www.skyviewwines.com. Free delivery with $100 minimum order to Manhattan and Bronx, $150 minimum to other boroughs, Westchester, and Rockland.

Recommended Passover Wines

Available at Skyview

BLANC DU CASTEL CHARDONNAY 2003 JUDEAN HILLS, ISRAEL $34.95
Melding notes of lemon butter, citrus, and pineapple with a dollop of new French oak, this wine is a ringer for a ripe-year Chassagne-Montrachet. Quite a trick, which Castel repeats year after year.

YARDEN SYRAH 2001, GALILEE, ISRAEL $19.95
Chocolaty aroma, then earthy and gamey in the mouth with fine tannins. Volcanic soil seems to give this wine a vivid yet refined flavor profile.

HERZOG SPECIAL EDITION CABERNET SAUVIGNON, CHALK HILL-WARNECKE VINEYARD 2000, CALIFORNIA $50
Ultra-dark in the glass. Cassis and pepper aromas. Deep and smooth, with olivey and herbal flavors that echo long in the mouth. From a top Sonoma vineyard, and it shows.

YATIR FOREST 2001 CABERNET SAUVIGNON, ISRAEL $44.95
An exciting new wine from a satellite miniwinery of Carmel, in a relatively new wine region near the Judean desert city of Arad. Sweetly ripe and plummy. Blistering hot days and cool nights bring on ripe, intense flavor without edgy tannins.