Klinefelter's syndrome is a chromosomal abnormality resulting in hypogonadism. Intellectual impairment and/or neuropsychiatric disorder are present in many cases. The variety of psychopathology accompanying the syndrome is reviewed from the literature and by case reports. The typical individual has a generalized inability to adapt, low social drive, lack of exploratory behavior, and emotional instability. He may also manifest a variety of neurotic, psychotic, and sociopathic behaviors that appear to be compensatory and individual in character.