The prize lot of Sotheby’s sale of Impressionist and Modern art next Wednesday is Picasso’s ferocious 1941 painting of his mistress Dora Maar. Estimated to sell for more than $50 million, it is just one of 10 Picassos in the sale – four of which were made after the artist turned 70.

A fractured but more straightforward 1937 portrait of Maar will carry a low estimate of $5 million next Tuesday at Christie’s. It is one of seven Picassos in the house’s Impressionist and Modern evening sale, which also includes a 1902 blue period portrait of one of Picasso’s earliest lovers, Germaine, estimated at $12 million to $18 million, and a 1967 “Mousquetaire,” estimated at $2 million to $3 million.

A renewed attention to Picasso’s accomplishments later in life (he died in 1973 at age 92) is bringing prices for the mature works closer to those for his earlier blue, rose, and Cubist periods. Works made after 1950 still are not approaching the $104 million world auction record for any work of art set by Picasso’s “Boy With a Pipe”(1905) in 2004. But demand for them is on the rise.

“Absolutely the market for late Picassos has strengthened considerably in the last two to three years,” the head of Impressionist and Modern art at Christie’s, Guy Bennett, said. He pointed to Christie’s sale last season of a 1954 portrait of Picasso’s 20-year-old neighbor Sylvette for $8 million, well above its $6 million high estimate. Another, more abstract 1954 portrait of Sylvette is estimated to bring between $4.5 million and $6 million at Sotheby’s next week. In 1995, the same portrait sold at Christie’s London for $850,000.

“There’s definitely been a big rise in late-period Picassos,” a co-director of Impressionist and Modern art at Sotheby’s,David Norman, said, identifying Picasso’s late period as post-1960. With time, Mr. Norman and other auctionhouse experts say, people will come to consider the artist’s late works in their proper context, rather than dismissing them as the products of an old man fiddling away, living off past glories.

“Now we’re in the 21st century, and people can understand and look back at 20th century and begin to see the importance of later works for a number of artists – Picasso, Miro – and you see a readjustment in what people are willing to spend,” Mr. Bennett said.

In addition, contemporary collectors looking to branch out are finding an affinity for the loose, Expressionist late Picassos, which seem to anticipate today’s gestural figuration. “A lot of late works by Picasso, Leger, and Miro look incredibly good with contemporary collections,” Mr. Norman said. “It’s new, young collectors who see them as dynamic, aggressive, and powerful enough.”

Picasso’s death in 1973 coincided with the youth or coming of age of many of today’s collectors.”It’s safe to say that for maybe 15 to 20 years after his death – and at the time of his death – his late work was underconsidered,” a codirector of Acquavella Gallery, Michael Findlay, said. Mr. Findlay pointed out that in the 1970s, David Hockney was among the few voices arguing for Picasso’s relevance as an artist of the 1960s. “Most people thought his late work was sloppy,” he said.

What once seemed sloppy today appears full of feeling. “Looking from our perspective now, the work seems to be powerful, colorful, with a kind of virility in the memory of a man who was in his 80s or 90s, exploring without any need to prove himself,” Mr. Findlay said.

Longevity can be a curse: An artist as prolific as Picasso is likely to gain detractors no matter what he or she does. By contrast, van Gogh, who died at 37, has not been the target of ageism or historical revisionism. His luminous 1890 portrait “L’Arlesienne, Madame Ginoux,” which he painted just five months before killing himself, anchors Christie’s sale and may also sell for more than $50 million. Christie’s expects the sale Tuesday to bring between $144.7 million and $197.4 million, while Sotheby’s is aiming for between $142.1 million and $197.7 million.

Picasso embodies the modern artist – a titan of longevity, inventive decade after decade, with a capacious biography to bolster the legend. Even for Picasso, however, taste is a fickle thing, and auction-house heads said the number of Picassos in any one sale is the luck of the draw. But consignors appear happy to satisfy the growing demand for late works.

At Sotheby’s, one of the sellers is the Metropolitan Museum of Art, which is shedding “Femme assise dans un fau teuil” (1960), estimated at $3 million to $5 million. In addition to the 1954 “Sylvette,” Sotheby’s is offering “Enfants dessinant” (1954), estimated at $2.5 million to $3.5 million, and “Arlequin au baton” (1969), estimated at $8 million to $10 million. “Two years ago people would have thought that’s an astonishingly high estimate,” Mr. Findlay said of the latter number. “But maybe now it’s okay.”

The “Mousquetaire” portraits of mustachioed cads vaulted in price when a large, Cubist 1968 version of a musketeer smoking sold for $7.2 million at Christie’s in November 2004. “Mousquetaire, buste” (1967), estimated to sell for between $2 million and $3 million at Christie’s,sold for $870,000 at Sotheby’s London in 1990. Christie’s is also selling “Femme se coiffant”(1956), a simply rendered portrait of Picasso’s second wife, Jacqueline, for an estimated $2.2 million to $2.8 million.

Picasso’s prolific output, according to the director of the Richard L. Feigen Gallery, Frances Beatty, actually buoys his market.”It has a kind of snowball effect. If there’s an artist with no supply, what’s the point?” she said.

Sotheby’s sales of Impressionist and Modern paintings on May 3 at 7 p.m. and May 4 at 10:15 a.m. and 2 p.m. Viewing times: April 28 & 29 and May 1 & 2 from 10 a.m. to 5 p.m.; April 30 from 1 p.m. to 5 p.m.; May 3 from 10 a.m. to noon (1334 York Ave., 212-606-7000).

Christie’s sales of Impressionist and Modern paintings on May 2 at 7 p.m. and May 3 at 2 p.m.Viewing times: April 28 & 29 and May 1 from 10 a.m. to 5 p.m.; April 30 from 1 p.m.to 5 p.m.; May 2 from 10 a.m.to noon (20 Rockefeller Plaza, 212-636-2000).