As the spring auctions begin, the stock market is rallying. But collectors and dealers are treading warily. Sotheby's stunned the art world three years ago by selling a single painting by Pablo Picasso for nearly $100 million. On Tuesday, the auction house says it will need to sell everything in its evening sale of Impressionist art to hit that mark.

Over the next two weeks, New York's chief auction houses -- Sotheby's, Christie's International and the smaller Phillips de Pury & Co. -- will try to protect price levels for dozens of the world's top artists at their semiannual sales of Impressionist, modern and contemporary art. With the recession hitting home among wealthy collectors, the auction houses are bracing for one of their toughest seasons in years.