Now we know that women and men can react differently to the same treatment, and that some treatments that work for men may not work as well for women, and some that work for women may not work as well for men. Women and men may have very different side effects from a drug, women may need a higher or lower dose of a drug to get the same effect as men, and devices that are designed for men's bodies may not fit women. Women may require different means of disease prevention than men. In addition, there are many diseases and conditions that only affect women, such as cancer of the uterus or ovaries, pregnancy, and menopause. Other diseases and conditions, such as osteoporosis, breast cancer, diabetes, and arthritis, affect more women than men. Women are needed for clinical research studies on these health conditions, so that new information can be gathered about how to prevent and treat them.More research is needed to understand women's unique health needs.