The present study was designed to evaluate the effects of long-term administration of testosterone enanthate (TE) on lipid and liver function parameters in rhesus monkeys (n = 9) maintained under controlled dietary conditions. Bimonthly administration of 50 mg of TE increased serum testosterone into the supraphysiological range one day after injection and peak levels were seen on day 3, followed by a decrease to above baseline values by day 14. High density lipoprotein cholesterol (HDL-C) levels decreased gradually; compared to baseline values, the decline was significant from the 19th month of injection until the first month of recovery. The increase in low density lipoprotein cholesterol (LDL-C) levels and the LDL-C/HDL-C ratio during the treatment period was not significant compared to baseline values; however, when compared to control animals, HDL-C and LDL-C levels and the LDL-C/HDL-C ratio were significantly elevated from the 12th month until the end of the treatment period. All lipid parameters recovered by the end of the treatment period. Control animals (n = 9) did not show significant changes in HDL-C and LDL-C levels and the LDL-C/HDL-C ratio during the study period. Total cholesterol levels decreased in control (n = 9) and treated animals from 6 to 15th months of the treatment period, coinciding with the feeding of sprouted grams to animals. TE injections did not change the levels of triglycerides, alkaline phosphatase or bilirubin in control and treated animals. However, transaminase (SGOT and SGPT) levels increased following TE injections and remained elevated until the end of injections followed by a return to baseline values or below during the recovery period. These effects could be due to the pharmacokinetic profile of TE in which testosterone levels were elevated to supraphysiological values after injections. The recovery of the TE-induced changes in lipid parameters and liver transminases is reassuring but the changes in these parameters during TE injections indicate the need for long-acting androgens with better pharmacokinetic properties.