For contemporary art dealers, summer means one thing: Roll out the group shows.

Group shows, in which either a gallery itself or an independent curator pulls together works by several artists, often under a slightly tenuous theme, are an accepted tradition of the slow summer months. Walking down West 25th Street this week, you would have seen no fewer than 27 of them, many with vague titles like “Hybridity/Ambivalence,””Urban Cosmologies,” and “World Without End.”

The reasons galleries do these shows are simple: First, with most serious collectors on vacation and the city quiet, “no artist wants to have a solo show” in the summer, the director of the Gagosian Gallery, Melissa Lazarov, said. Second, a group show offers galleries a commitment-free way to get to know emerging artists and find new ones to represent.

Finally, a group show generally takes less effort than a solo show, especially with an independent curator — and the slow months of July and August provide a rare chance for dealers to relax. “The art season now is nearly ten months long,” the director of the Paul Kasmin Gallery, Hayden Dunbar, said.”In May there are the auctions, in June the art fairs and European auctions. Before you know it, it’s the end of July and you haven’t had a chance to catch your breath. And then, boom — you’ve got a show opening the week after Labor Day.”

Lots of galleries pull together group shows from their own stable of artists.”Those are really just low-effort,” the director of the Plus Ultra Gallery, Edward Winkleman, said.

Some come up with gimmicks that minimize their workload.The Andrew Kreps Gallery, for instance, has a show up called “Two Friends and So On” — a reprise of a concept it first tried out in 2000. In this incarnation, the gallery asked the artists Jonathan Horowitz and Rob Pruitt to together invite a friend to join the show, who in turn would invite another friend, and so on. A show like that pretty much curates itself.

Allison Cave, who now works at Harris Lieberman, in Soho, remembers that when she was at Lombard-Freid Projects, they did a group show called “Friends and Family,” to which gallery staff, as well as friends and family, were invited to contribute.

As for conventionally curated group show themes, they range from the vague or semantic — “Dereconstruction,” “Matter of Time” — to the very literal. A former gallery owner who is now the president of the Lower Manhattan Cultural Council, Tom Healy, wrote in an e-mail that he once exhibited a show, curated by the writer Wayne Koestenbaum, called “Bathroom,” consisting entirely of works related to that room.”A vandal shattered a porcelain Gavin Turk basin and someone peed on the floor,” Mr. Healy wrote.The artists were a little touchy, too: “One artist who made lace toilet seat covers objected to being next to a Mapplethorpe Polaroid of a boy and his erection.”

Mr. Winkleman said that he has often found themed shows “hyper-clever” and superficial. “The curators are pursuing their own agendas,” Mr. Winkleman said, “and it seems like the goal is to have the quippiest, wittiest take on the themes from throughout the year.”

Asked for an example, Mr. Winkleman, in the spirit of humility, offered up one of his own curatorial efforts, a show called “The Cool Show,” with the subtitle “Refrigerate After Opening.” “It was about a cutting-edge, cold, icy aesthetic,” he said. “The title was witty and clever, but the show was about an inch deep.It wasn’t really fair to the artists because it didn’t say anything about their work other than that, in a very superficial way, they could be grouped like this.”

But the taste for hyper-clever themed shows may be passing, Mr. Winkelman said.Paul Kasmin, for instance, just closed what might be called an anti-theme show. Curated by the artist Jack Pearson, it was titled: “The Name of This Show Is Not: Gay Art Now.” “It’s an example of the backlash,” Mr. Winkleman said. “What this says about the group show is, they were all surface and no depth.”

“Gay art was something that was sort of thought highly of in the early 90s, and this show was a comment on that,” Mr. Dunbar said. “You don’t have to be gay to make great art.”

But the group show is not only about dealers taking a break and curators pursuing trendiness. It’s also, from the dealers’ side, an opportunity to get to know new artists and, from the artists’ side, a chance to find representation.

“I don’t usually do gallery artists in the group show,” Larissa Goldston, of Larissa Goldston Gallery, said. “They tend to be artists that I’m considering or artists whose work I find interesting, and I want to feel out the dynamic in the space.” She has already decided to represent one new artist from her current show, G.Bradley Rhodes. She described the show, called “Let’s Talk About … ,” as about “things that are really male”: cars, subwoofers, war, sex.

“Most people who are in a group show are really excited to be in a show,” Ms. Goldston said. And the opportunity to have their work seen can make a huge difference, she explained. A curator who came into the gallery this summer liked the work by one of the youngest artists, Audrey Chan, and picked her to be in a major show in France.

As entrenched as the July–August group show is, recently some younger galleries have bucked tradition and put on solo shows in the summer. With everyone else either closed or exhibiting a group show, a solo show in August can attract a lot of attention. Zach Feuer Gallery, on 24th Street, has been closed for renovations and is reopening on August 8, with a big solo show of the photographer Stuart Hawkins.

Asked why he decided to do a solo show in August, Mr. Feuer said,”People are still here in the summer, and there’s no reason that we should ever not do a serious show. In some ways, everyone else taking a break just makes it a little easier for us: It’s easier for a young photographer to go up in August or September and not compete against an Andreas Gursky show that would go up in November.”

Does he think he’ll start a trend, bringing more serious shows to the summer? “I hope not — I like having one of the only solo shows up in the summer,” he said.