Six drugs classified as anabolic steroids and capable of producing appreciable nitrogen retention in the body were studied with respect to their effects on the activity of the liver. Four tests of liver function (sulfobromophthalein retention, serum bilirubin, serum lactic dehydrogenase, and total creatinine chromogen) were applied in 38 healthy men. The steroid most used was norethandrolone, given intramuscularly. In addition a comparison between intramuscular and oral routes of administration was made in 16 convalescent patients. Norethandrolone was found to be the most toxic of the 6 steroids tested. All increased the retention of sulfobromophthalein and the excretion of creatinine; none affected the serum bilirubin. The route of administration did not make a significant difference.