The name Clamp may sound odd and unfamiliar to Western ears, but this four-woman studio ranks among the most successful creators of manga, or graphic novels, in Japan and the United States. Over the last 17 years these women — Satsuki Igarashi, Apapa Mokona, Tsubaki Nekoi and Ageha Ohkawa — have produced 22 popular manga series, many of which have been adapted to animation, including “X,” “Chobits” and “Cardcaptor Sakura,” all available on DVD in the United States.

“Clamp have been an integral part of the manga explosion that’s occurred in the U.S. over the past several years,” said Dallas Middaugh, associate publisher of the Del Rey Manga division of Random House, in an e-mail message. “Their fluid, dramatic artwork and storytelling style struck a strong chord with male and female manga readers.”

More than one million copies of the “Tsubasa” manga have been sold in the United States, and next month Del Rey will publish a character guide to that popular series. The Houston-based FUNimation Entertainment recently announced that the 52-episode animated television program based on “Tsubasa” would be available on DVD in this country early next year.

When they discuss their work, the four artists of Clamp confer among themselves; then Ms. Ohkawa usually acts as spokeswoman.

Through an interpreter, Ms. Ohkawa explained in an interview that the studio began as a group of 11 art students who got together to create doujinshi, or fan comics: amateur publications that continue the adventures of popular animated and/or manga characters. No one remembers who chose the name Clamp, but it stuck, long after the group shrank to four members who became professionals.

The women seem both pleased and surprised at their popularity in the United States. “For some series, we do consider the international audience,” Ms. Ohkawa said. “But we wonder, when American girls read our manga, do the stories touch their hearts? Can they relate to the characters?”

Clamp has created a diverse body of work in an industry in which artists often specialize in a single genre. The sci-fi comedy “Chobits” involves a frustrated romance between a geeky college student and a disturbingly beautiful android. In “xxxHOLIC,” Watanuki, a psychic high school boy, blunders into the shop of Yuko, a sorceress who can supply whatever a customer most ardently desires. Clamp’s best-loved creation is “Cardcaptor Sakura,” the story of a fourth-grade girl who inadvertently releases a deck of enchanted cards, then has to retrieve them before they work mischief on the world.

Unlike Serena, the ditsy teenager who transforms into Sailor Moon, the heroine of another popular series, Sakura is a good-natured but never saccharine girl who learns and grows from her supernatural experiences. Her best friend, Tomoyo, makes cute costumes for her magical missions.

“It’s common in girls’ manga for a character to transform, as Sailor Moon does, and we wanted to incorporate that into ‘Sakura,’ ” Ms. Ohkawa said. “But many of them always wear the same outfit, so we wanted to add a twist. We feel it’s pretty sad for a girl to wear the same outfit all the time.”

Clamp’s manga are also distinguished by their diverse visual styles. Yuko, the sensual sorceress in “xxxHOLIC,” might have stepped out of a wood-block print. Kamui, the slender, androgynous hero of the dark fantasy “X,” seeks the advice of Princess Hinoto, whose hair flows in Art Nouveau swirls that recall Alphonse Mucha’s widely reproduced posters for Sarah Bernhardt and Job cigarette papers. The massed blacks and dark shading in “xxxHOLIC” contrasts sharply with the straightforward line work of “Cardcaptor Sakura.”

Ms. Ohkawa, who compares her role to that of a producer-director, explained: “I decide who does the characters, and what she’s going to do with them, as a director would pick his actors. I assign the roles, depending on the genre of the series: horror, comedy and so forth. I also choose the visual style: in the case of ‘xxxHOLIC,’ it’s derived from Ukiyo-e,” woodblock prints.

“However, I’m not sure if the staff is satisfied with my direction,” she said with a laugh.

Many of the most popular manga on both sides of the Pacific are written and drawn by women, including Rumiko Takahashi (“Ranma 1/2,” “InuYasha”); Hiromu Arakawa (“Fullmetal Alchemist”); and Clamp. Their many hits have given the Clamp artists the power to create pretty much whatever they choose.

“While it’s true that the number of female directors in the animation industry has increased over the years, it’s more common for women artists to present their work in manga,” Ms. Ohkawa said. “It’s a way for them to express themselves freely. Strong female characters have become very common in manga — Sailor Moon is probably the most famous example — but I don’t know that women in Japan have become stronger. We’re in a unique position: Clamp makes a presentation to the publishers about what we want to do, receive an approval and go to work.”

The Clamp artists were eager to discuss the differences between the Japanese and American approaches to the creation of comics and graphic novels, and the growing cross-pollination between the popular cultures of the two countries.

“In Japan the artists on a manga don’t change until they complete the series, and when the artist passes away, the story ends; there’s just one artist,” Ms. Ohkawa said. “But in America, different teams work on different stories for ‘X-Men’ and other comics.”

“It used to be difficult to find American comics in Japan, but they’ve become more accessible in the bigger bookstores,” she said. “As creators in Japan, we’re very curious about American work and are pretty sure we’re influencing each other.”