The effects of the severity of psychiatric illnesses on thyroid function and their relationship to serum testosterone levels were studied in 38 men of African origin, suffering from chronic schizophrenia. Significantly lower levels of serum T4, T3, FT4I and testosterone in acutely psychotic patients indicated decreased thyroid-gonadal activity. Higher serum T4 and FT4I and lower serum TSH, testosterone and cortisol levels were observed in patients whose illnesses were in remission. Levels of both FT4I and testosterone in clinically stable patients, however, were not significantly different in comparison to controls, suggesting recovery from the illness. No significant differences either in thyroid or gonadal hormones were observed between patients exhibiting depression or elated affects; among disorganized, catatonic, paranoid and undifferentiated types; and among patients treated with different psychotropic drugs. The possible mechanisms involved in such thyroid-gonad relationship are discussed.