To examine the influence of cigarette smoking initiation on serum lipid and lipoprotein changes in early life, 747 nonsmoking 9- to 17-year-olds from the biracial community of Bogalusa, Louisiana were reexamined five to six years following an initial screening. Upon reexamination in 1981-1983, 147 reported smoking cigarettes (mean duration, 3.5 years; median number of weekly cigarettes, 20). Compared with nonsmokers, persons who began smoking had more unfavorable changes in serum triglycerides and lipoprotein cholesterol levels during follow-up, independently of age, sexual maturation, obesity, alcohol consumption, and oral contraceptive use in females. Smoking initiation was not associated with increases in serum total cholesterol levels, but compared with nonsmokers, white males and white females smoking three or more packs weekly showed additional mean increases of 13.2 and 11.6 mg/dl in low density lipoprotein cholesterol, additional 5.9 and 2.4 mg/dl increases in very low density lipoprotein cholesterol (VLDL-C), and additional decreases of 15.6 and 9.2 mg/dl in high density lipoprotein cholesterol levels, respectively. Black smokers showed larger increases in serum triglycerides and VLDL-C levels than did black nonsmokers. These findings indicate that the start of even modest cigarette smoking may have potentially long-term atherogenic effects. Prevention of smoking in early life should therefore be an important aspect of cardiovascular disease intervention.