Zinc administration in rats is associated with a rise in serum cholesterol level. This study examined the effect of zinc administration on serum lipoprotein values in man. Twelve healthy adult men ingested 440 mg of zinc sulfate per day for five weeks. High-density lipoprotein-cholesterol concentration decreased 25% below baseline values (40.5 to 30.1 mg/dL). Total cholesterol, triglyceride, and low-density lipoprotein-cholesterol levels did not change throughout the study. The sharp fall of the "antiatherogenic" lipoprotein, high-density lipoprotein, associated with zinc administration supports the concept that zinc ingestion may be atherogenic in man.