1. Serum lipid concentrations were measured in groups of women who had undergone oophorectomy and hysterectomy or hysterectomy alone. Measurements were repeated in some of the oophorectomized women after treatment for 1 year with either mestranol or a placebo.
2. A significant correlation was found between serum cholesterol concentrations and age in the women with intact ovaries. Although such a correlation was not apparent in the oophorectomized women, the younger women in this group had significantly higher cholesterol concentrations than the younger women with intact ovaries.
3. A significant correlation was found between serum triglyceride concentration and age in both groups of women, but the oophorectomized women showed a significantly slower rate of increase of triglyceride with age than women with intact ovaries.
4. Administration of 20–40 μg of mestranol daily for 1 year was associated with a significant fall in serum cholesterol and a significant rise in serum triglyceride.