If auctions are the major leagues of art-as-spectator-sport, then the catalogues are the scorecards. This week the glossy volumes containing the Impressionist and Modern work will land in collectors’ mailboxes, and potential buyers will flip through the heavy-stock pages to take note of prices, provenance, and the shifting supply of sought-after art. Close reading of the catalogues explain which artists are in play — and which ones are rapidly gaining in price.

After the rollicking London season in February, the upcoming New York season promises more excitement — especially for the work of recent rapid gainers including Amedeo Modigliani, Lyonel Feininger, Ernst Ludwig Kirchner, and Egon Schiele. Pablo Picasso and Willem de Kooning are proving that even the most established artists can have a run-up in price, too.

According to Artnet, an online service that tracks auction sales around the world, the average sale price last year for a Modigliani was nearly $3.5 million — triple the average price the artist fetched in 2005. With 29 Modiglianis sold at auction in 2006, the number of paintings traded last year reached a level not seen since 2001, when his average prices were around $675,000.

German Expressionists are gaining significant ground. In 2006, the average prices for Kirchner shot up 643.5% with a third more lots sold than the previous year. At Christie’s last November, a Kirchner Berlin street scene — a prized work — fetched $34 million. This time around Christie’s has a 1910 nude estimated between $12 million and $18 million. Feininger sold 116 paintings at auction in 2006, a huge increase driven by the 556.5% growth in average prices over the last three years. Sotheby’s has a canvas of his for sale next month.

“For a long time they were artists owned by European collectors and primarily sold in Europe,” Sotheby’s Contemporary art expert Anthony Grant said. “Now international collectors realize they must have representation from these artists.”

Adding to that, in the current market, there are two types of collectors, according to Christie’s Postwar Art expert Brett Gorvy. Established market players are willing to buy an exceptional work at almost any price, while new collectors are attracted to beautiful, iconic art. In both cases, the collectors seem happy to ignore the previous structure of prices and pay whatever it takes to outlast other bidders.

One boon to the American market has been the presence of New York’s Neue Galerie. The museum and its primary patron, Ronald Lauder, have bought a number of these artists. But its shows seem to be having a positive effect on prices for German and Austrian painters. “The Neue Gallerie has a lot to do with it,” art adviser Nicholas MacLean said. “They have educated the market.”

Art history drives collectors but so does scarcity — and beauty. Schiele’s market was given a boost by the sale last year of several paintings that were on the market as the result of restitution. What is remarkable about the popularity of Schiele is not that the artist had such a brief career but that his most prized pieces are not canvases but works on paper. This is “beautiful, rare, romantic material that appeals to a broad audience,”Christie’s Post-War Art expert Brett Gorvy said. “The prices are generally higher for the works on paper because they are gorgeous works of women that are very beautiful and highly erotic.”

Obviously, sex sells. Schiele’s average price was nearly $2.2 million last year, representing a one-year jump of 586.4%. Picasso’s erotic late work has also seen a significant rise in the market recently. His work dominates the art market because of his prolific output and outsized fame. Even in America, where a quarter of the lots in Sotheby’s spring Impressionist and Modern sale are works by Picasso, there has been room for growth in price.

“It was a furtive flurry of activity at the end of this man’s life,” art consultant Abigail Asher, said. “It was incredibly sexual and it was bold. A lot of people pooh-poohed it and dismissed it. Then they looked at it and said it’s amazing for a man of that age.”

“Anything from 1960 on,” Sotheby’s Impressionism and Modernism expert, David Norman, said, “was considered the sloppier flailings of a major artist.”

Then two things happened. First, collectors sniffed out the value and re-evaluated the work. Second, contemporary art collectors conditioned by Francis Bacon and Jean-Michel Basquiat took a look at the maestro’s later work. The raw quality took on a new meaning to them. “A 1965 Picasso next to a Bacon or Basquiat looks relevant and much more essential these days. It can be a foundation of the collection,” Mr. Norman said. “But now the prices have quintupled.”

De Kooning is another artist whose prices looked like they couldn’t go higher. His seminal works from the 1950s have fetched as much as nine figures in private sales. He was so prolific, however, that his oeuvre also contains under-appreciated areas. “The great 1970s landscapes had clearly been undervalued,” Ms. Asher said. “There’s no question about that.”

But the rise in prices for those canvasses set off a chain reaction. When the work from the ’70s began to reach the $20 million range, “that pulled up the 80s pictures,” Ms. Asher said. “Collectors saw Gerhard Richter abstracts selling for $3 million and asked how a 1980s de Kooning could be $1.8 million.”

And the market took care of the rest.