Patches and gels are already known to be effective for relieving the hot flashes and sleep-interrupting night sweats that plague many women. No one knows whether they will prove safer than pills in terms of breast cancer, heart attack or stroke risk. A large study currently under way may answer that.

But if they do, it may soften some of the backlash against hormones since a landmark study in 2002 frightened many women away from their use. Critics of that study have long contended it is the type of estrogen or progestin, the dosage, and the method of taking the hormones that may affect the health risks.

"Part of the reason we think oral estrogens do cause clots is that they pass through the liver and can cause some clotting factors to be produced," said Dr. Karen Bradshaw, director of women's health and an endocrinology specialist at UT Southwestern Medical Center.

Hormones through skin patches are directly absorbed into the bloodstream, and therefore can be given in far lower doses to be effective, she explained.

"This study, like others, may change things" in terms of what hormones women and doctors are willing to use, Bradshaw said. Before the Women's Health study, Prempro and Premarin accounted for half of the hormones she prescribed. Now they account for about one-fourth, and much of that is the lower dose of Prempro that Wyeth began selling in 2003, a year after the Women's Health study.

The study tested Wyeth's Prempro and Premarin, which contain synthetic estrogens made from the urine of pregnant horses. Some people believe estrogens from plant sources are closer to what the human body naturally produces and may be safer. The plant forms are in many competitors¡¯pills and also in patches, creams and gels.

The French researchers compared 271 women ages 45 to 70 who suffered blood clots to 610 similar women without clots. Women taking various hormone pills were more than four times more likely to suffer clots than women not taking hormones or receiving them through patches, gels or creams.

Millions of women abandoned hormone pills after the Women's Health Initiative study reported in 2002 higher rates of stroke among those taking estrogen, and of stroke and breast cancer with estrogen-progestin use.