We investigated effects of a hypocaloric diet of 5023.2 kJ (1200 kcal) on body weight and plasma lipids in 40 obese female subjects in two groups: (1) 20 obese subjects with normal plasma triglycerides at the onset (means = 148.5 mg/dl), and (2) 20 with hypertriglyceridemia (means = 225.3 mg/dl). The hypocaloric diet was instituted for a mean period of nine months and average body weight loss was 15.6 kg for Gp 1 and 14.0 kg for Gp 2. In Gp 1 there were no significant changes in total plasma cholesterol or triglycerides, but HDL-cholesterol rose significantly from a mean value of 42.5 to 53.6 mg/dl (P less than 0.001). Subjects in Gp 2 showed a significant decrease in plasma triglycerides (from 225.3 to 152.3 mg/dl, P less than 0.001) and an elevation in HDL-cholesterol from 41.2 to 48.2 mg/dl, P less than 0.001. Our results show that losing weight is associated with HDL-cholesterol elevation, independently of variation in plasma triglycerides.