There are gender-related differences in the prevalence, course and treatment response characteristics of schizophrenia and mood disorders. Gonadal steroids exert potent effects on mood, cognition and behavior, and there is little doubt that androgens are crucial for differentiating to each gender. Serum level of total testosterone, free testosterone, estradiol and sex hormone binding globulin was measured in 69 medication-free men with either schizophrenia (n = 29) or bipolar I disorder, manic episode (n = 18) or major depressive disorder (n = 22). There was a statistically significant difference in free testosterone level between mania and schizophrenia groups (p < 0.05). The higher free testosterone level in the mania group compared to the schizophrenia group found in this study supports further investigation of a potential difference in the hypothalamic-pituitary-gonadal axis between patients with schizophrenia and bipolar I disorder, manic.