The global taste for modern masters helped the market for Impressionist and modern art continue its upward climb at Christie’s on Wednesday night, where record prices were reached for artists like Matisse and Gris.

The evening’s auction, the second of the week, illustrated how — with supplies dwindling and the number of new collectors growing — many buyers are finding the marketplace particularly competitive, even for works that are not considered top flight.

The evening sale was overstuffed with paintings, drawings and sculptures of varying quality, and considerably larger and longer (way too long, many in the audience were grumbling) than the one at Sotheby’s the night before. From the start, the Sotheby’s auction had a clear winner, a 1917 Modigliani nude, which brought $68.9 million, a record for the artist at auction.

Christie’s had one too, it turned out, though the professionals weren’t so sure before the sale began. But five bidders jumped in to bring home Matisse’s monumental bronze sculpture of a woman’s back — “Nu de Dos, 4 État (Back IV)” — conceived in 1930 but not cast until 1978. The superdealer Larry Gagosian won the sculpture for $48.8 million, a record for the artist and well above its $35 million high estimate. After the sale Mr. Gagosian said he had bid on behalf of a client whom he declined to name. (Mr. Gagosian has bid in the past for Steven A. Cohen, the hedge fund billionaire, who was seen in a skybox above the salesroom at last night’s auction.)

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