Two fasting lipoprotein cholesterol measurements have been made on Framingham Offspring Study participants, first in 1971-75 and again in 1979-83. Longitudinal analysis (n = 2433, age 20-49 at first exam) using multivariate regression found aging, weight gain, vasectomy, menopause, and increased smoking are associated with worsening lipoprotein profiles, while increased alcohol consumption is associated with increased high density lipoprotein cholesterol (HDL-C). Average increases in low density lipoprotein cholesterol (LDL-C) and very low density lipoprotein cholesterol (VLDL-C) in women accelerate with age; in men the increases are similar or perhaps decelerate with age. Secular trends were measured using age-adjusted mean values for individuals aged 25-54. Averages of total cholesterol, LDL-C (men only), systolic and diastolic blood pressure, body mass index, number of cigarettes per day, and alcohol consumption were lower at the second examination. Two secular trends in women indicate a possible worsening of population lipoprotein profiles: mean VLDL-C was higher and mean HDL-C lower at the second exam.