We examined the relationships of cigarette smoking with fasting triglycerides, total cholesterol, and high-density lipoprotein cholesterol (HDL-C) levels among a group of 191 white women aged 20 to 40 years. The mean triglyceride level among current smokers was 100.0 mg/100 ml and among nonsmokers was 68.4 mg/dl (p less than 0.005). Mean total cholesterol values among current smokers and nonsmokers were, respectively, 197.0 and 189.1 mg/dl (p less than 0.1). Mean HDL-C levels were 45.0 mg/dl among women who were smoking and 52.1 mg/dl among nonsmokers (p less than 0.005). Simultaneous adjustments for the effects of age, weight, height, blood glucose, resting pulse, and oral contraceptive use did not materially alter these relationships. A modest portion of the effect of cigarette smoking on risk of coronary heart disease may be explained by an adverse effect of cigarette smoking on blood lipids.