The effects of large doses of anabolic steroids on 24-hour blood pressure, cardiac structure and function, and lipid profiles were studied in 10 body builders using anabolic steroids and 14 body builders who did not use steroids (control subjects). All subjects underwent noninvasive 24-hour blood pressure monitoring, echocardiography, Doppler analysis of transmitral flow, and analysis for lipoprotein and gonadotropin levels. Anabolic steroid users were studied at the end of a steroid cycle and after a period of withdrawal. Average 24-hour blood pressure was similar in the two groups, but anabolic steroid users exhibited a smaller pressure reduction during sleep than did nonusers. This finding was present both at the end of treatment and after the period of withdrawal. Echocardiographic dimensional and functional indexes did not differ substantially between anabolic steroid users and the nonusers, and were similar in anabolic steroid users during use and after withdrawal. Anabolic steroid users also had higher LDL and lower HDL cholesterol levels than nonusers; Lp(a) was higher in nonusers, although this difference did not attain the level of statistical significance. These differences were more striking at the end of the treatment period. The results of this study show that chronic anabolic steroid intake causes an abnormal 24-hour blood pressure pattern, characterized by a flattening of the diurnal curve, and minor changes of the dimensional echocardiographic parameters.