In a 20-year prospective study of the influence of lifestyle and age on health parameters in men's and women's serum cholesterol, triglycerides and high density and low density lipoproteins were measured periodically to determine each person's longitudinal profile. The accumulated data for 1008 women of 20 to 70 years is averaged by five-year age brackets. Scatter plots and simple regression of these five-year group means for ages 20 to 45 years, reveals a gradual increase in serum cholesterol, increasing from 176 mg/dl to 196 with a slope of 0.61 mg/dl per year. Between ages 45 and 70, the slope increases substantially to 1.91 mg/dl per year, and the five-year group means rise from 196 at age 45 to 239 at age 70 in rather uniform increments. The data have been analyzed for the other lipids and the relationship to estrogen replacement, nutritional, and exercise habits.