The aim this this study was to determine that administration of single higher dose nandrolone decanoate (40 mg/kg) on serum IL-1β, TNF-α, IL-10 and IL-6 levels and some biochemical parameters during 24 h in male and female rats. The blood samples were taken from 5 male and female rats to obtain their starting values. Then the blood samples were taken from 6 rats in sampling time at 1st, 2nd, 4th, 8th, 12th and 24th h following the nandrolone decanoate administration. There were significant increases determined in the serum IL-1β levels, numerical increases in the TNF-α levels whereas decreased IL-6 levels were determined. IL-10 levels did not change during experimental period. While serum GGT and BUN levels increased towards the last h of the study, increased ALP levels were observed only female rats. There was no any significance changes were determined in the other biochemical (ALT, AST, CKMB and LDH) values. As a result, increased IL-1β and TNF-α levels, proinflammatory cytokines, and some biochemical parameters may be reflect that long term used nandrolone decanoate causes organ damages and effect immune system function. However, effects of long term used nandrolone decanoate on the immune system and organ functions should be detailed evaluated.