One hundred and twenty male albino rats weighing 180–200 g were used to determine the effect of anabolic steroid hormones on adaptive changes in the synthesis of ribosomal RNA both in sedentary animals and in animals involved in a training program. One injection of Retabolil (0.1 mg/100 g body weight) increased the α-amanitin insensitive RNA polymerase activity of nuclei from skeletal muscles. Fourteen h after this hormone injection the enzyme activity was 45% higher than in control animals and it remained at this level for 4 days. Under these conditions a selective binding of 19-nortestosterone with cytoplasmic proteins of skeletal muscle was found. Physical training increased the RNA polymerase activity by 40% (P<0.05). It was found that the testosterone binding capacity of a cytoplasmic extract from trained animals was 70% greater than that of the control animals (P<0.05). Four injections of Retabolil during training resulted in an additional increase of RNA polymerase activity of 40% (P<0.05) but reduced the testosterone binding capacity of the cytoplasmic proteins that occurred with training by 21%. The findings demonstrate the effect of anabolic hormones in the regulation of RNA synthesis in skeletal muscle nuclei in the process of their adaptation to systematic physical training.