The Women's Health Initiative (WHI), the largest-ever clinical study on women's health in the United States, began a new stage of recruitment last week, adding 24 new clinics to continue studying cancer, osteoporosis and heart disease in women.

These new clinics are the second phase of WHI, which has already opened 16 "Vanguard Clinical Centers," including one at Brigham and Women's Hospital, one of Harvard's teaching hospitals.

The WHI will study the effects of low-fat diets, post-menopausal hormone-replacement and vitamin supplements on heart disease, osteoporosis, and colon, rectal and breast cancers. It aims to recruit a total of 160,000 American women between the ages of 50 and 79.

The National Institutes of Health in Bethesda, Md. provided a $625 million grant to fund the 40 centers, with plans for the study to continue 15 years.

The 24 new clinics that opened last week are located throughout the country and will begin their clinical studies by January.

When the Boston clinic opened last September, it received a flood of replies from women who wanted to participate in the study.

"We have had a very phenomenal response from women in the Boston and New England area," said Kate L. Kalan, clinic manager of the Vanguard Center at Brigham and Women's. "[We received] several thousand phone calls in the first few days of recruitment."

The largest previous study of women's health, the Nurse's Health Study, was restricted to registered nurses, according to hospital officials. The WHI is the first major study of its kind open to the public.

Kalan said the new study is more "face-to-face" than its predecessor, with 1,400 of the volunteers receiving clinical care through the program.

"American women have really wanted this to happen," said Associate Professor of Medicine Dr. JoAnn E. Manson, the clinic's principal investigator.

Though the results of the study may not directly affect the women involved, Kalan said, "they recognize that they're really doing it for their daughters and granddaughters."

In the Boston area alone, 400 women are participating in WHI on a variety of levels.

"The commitment varies by clinical trial. The women who are randomly assigned to the 'low-fat active treatment' portion, for example, undergo intensive nutrition counselling.... They attend meetings once a week for the first six weeks," Manson said.

These women, who learn how to shop for and cook low-fat meals, "are tremendously enjoying what they are learning," according to Manson.

Women interested in volunteering for the study can call 278-0782 for more information.