Half of the subjects were randomized to diet instruction with two years of follow-up and half to six months of no intervention followed by the same diet instruction and followup. Control subjects had a fasting blood drawn at three months of the nonintervention period. Having parallel intervention and control groups was necessary to test the efficacy of the NCEP Step Two Diet: The diet was taught to study subjects during eight weekly two hour classes. Follow-up included four individual visits, at three, six, nine, and twelve months, with a dietitian and two group sessions, at 4.5 and 10.5 months, in the first year and two individual visits, at 18 and 24 months, in the second year. Fasting blood samples for lipoprotein lipid analysis and 4-day food diaries were collected at all individual visits. Additionally, medical history, lifestyle characteristics, vital signs, other adherence measures, behavioral factors related to adherence, and serum nutrients for monitoring nutrient sufficiency were collected. Dietitians provided adherence and dietary modification counseling as necessary to help participants maximize their adherence. The primary questions to be answered were: 1) Did the NCEP Step Two Diet effectively lower plasma lipids in hypercholesterolemic (HC) and combined hyperlipidemic (CHL) women and men over six months? 2) Did HC and CHL women have a different response than HC and CHL men? 3) Was response in women influenced by menstrual status and sex hormone exposure?, and 4) Were the behavioral adaptations to dietary modification different between women and men?