Sometimes you can learn just how serious a wine merchant is not by what he wants to sell you but by what he hesitates to ring up. I realized as much last week, at PJ Liquor Warehouse, a vast, bare-bones discounter on a faded section of Upper Broadway. In a dusty bin at the far corner of the selling floor, I’d come across a seemingly long-forgotten single bottle of a Pommard, Premier Cru, a fine red Burgundy, from the 1993 vintage. More than a decade old, the wine promised to be in its prime of maturity. But when I checked out, the cashier was unable to find a price for the bottle in the computerized inventory. She called over the 38-year-old proprietor Peter Yi, who had no better luck.

“Make me a fair price,” I said.

Mr. Yi slowly turned the bottle over in his hands. “Does $35 sound fair?” he asked.

That’s when I had my insight into this unflashy but very serious wine merchant. “It’s fair,” I said. “But I get the feeling you’d rather drink this Burgundy yourself instead of selling it to me, right?” Mr. Yi nodded. As a rule, you can trust a wine shop where the proprietor “unsells” a wine so that he can enjoy it himself.

Nothing about PJ’s suggests that it is one of the city’s finest wine resources – not the giant “Liquor Warehouse” sign, certainly, or the long center aisle stacked with cases of flavored liqueurs and brandies in neon tints undreamed of in nature. But there are more than 4,000 wines on display as well. Beginning at 2 p.m. each Thursday, wholesalers arrive to submit wine samples to a staff panel led by Mr. Yi in a tasting room at the rear of the store. New suppliers have 60 minutes to present six wines while established suppliers get 90 minutes to submit 12 wines. The tastings go on nonstop until 9 p.m. Only a small number of the wines tasted make it to sales floor.

Last Friday afternoon, I noticed 20 bottles wrapped in brown paper bags on the tasting table. “They’re all California Pinot Noirs that we’re about to taste,” Mr. Yi said. “We’re looking for the best ones in different price ranges. Want to join us?”

Your intrepid columnist did not shirk his duty. Along with Mr. Yi and his three-member tasting panel, I sampled the wines in two flights, one limited to wines selling for less than $15, the other to wines selling for more than $30. A third flight of wines between $15 and $30 had been previously tasted. The winners will soon be on sale at PJ’s (the name is made up of the first initials of Peter Yi and his wife, Jennifer, who handles the administrative side of the store).

As a student, Mr. Yi helped out his Korean-born father in the family-owned liquor store in Astoria, Queens. Mr. Yi chose accounting as a career, but a few years into his first job, his father called to ask him if he wanted to manage a liquor store he had just leased on West 207th Street in Manhattan. By then, Mr. Yi had experienced a wine revelation: a great bottle of Clos de Vougeot from Burgundy, at a restaurant. He was ready to switch careers. At the 207th Street store, Mr. Yi quickly expanded sales volume. When the lease expired in 1996, he moved around the corner to his current, far larger quarters in a former piano-repair workshop. In most storefront liquor shops, deliveries must come through the same entrance as shoppers. Adapting this new store to high volume sales, Mr. Yi built a separate door with a conveyor belt for deliveries and air-conditioned the basement for wine storage.

Broadway at 206th Street is not a location favored by free-spending wine collectors. Mr. Yi’s primary strategy to attract wine customers from other neighborhoods is to beat competitors’ prices. While most wine shops operate on 50% markups, PJ’s is closer to 25%. What has really made the business grow, however, is its well-made Web site, which debuted in 2000. Currently, according to Mr. Yi, more than half of PJ’s wine sales are made through the Web site to customers in more than 35 states. A consultant works full-time maintaining the Web site.

While PJ’s has a solid inventory of French, Italian, and American wines, its greatest depth is in Spanish wines. I don’t know of any other local wine seller that can outdo PJ’s selection of 11 different wines from Bierzo, a little-known yet superb wine region in northwestern Spain, or that can rival PJ’s array of 43 different sherries, a favorite of Mr. Yi. “Sherry is my mission,” he said. PJ’s is reputedly the country’s largest seller of Lancers, the spritzy Portuguese wines packaged in clay crocks that were all the rage in the 1970s. Each April, Mr. Yi heads to Bordeaux to taste the new vintage and selects “futures” to be sold at prices that are lower than others I’ve found. The currently offered 2003 futures are scheduled for delivery in spring 2006.

PJ’s offers a Wine School, whose spring session is already under way, but a four-evening mini-course begins on March 28 with a “power tasting” of 20 wines from Europe’s classic wine regions.” Conducted by wine educator Michael Green, the course is held at Astra New York in the D&D Building at 979 Third Avenue. The cost is $125 a session by check, or $132 by credit card. For more information, call 212-877-1015.

PJ Liquor Warehouse, 4898 Broadway, 212-567-5500, www.pjwine.com.