In 43 men who required further examination of erectile function, we analyzed the relationship between the various factors including hormone levels, penile blood pressure index (PBPI), shape of the arterial wave, erection period after prostaglandin E1 injection and dynamic cavernosography/metry, as well as the patterns of nocturnal penile tumescence (NPT) with rigidity. Normal, dissociation, short episode, low amplitude and flat trace patterns, which were classified by Kaneko, were observed in 11, 8, 11, 2 and 11 men, respectively. Uncoupling was not observed in any men. There were no differences in the levels of prolactin and LH among the 6 patterns. A high FSH level was seen in men with a flat trace pattern; a low level of free testosterone ( < 12.2 pg/ml) was seen in men with dissociation, low amplitude and flat trace patterns, and low PBPI ( < 0.75) in men with flat trace pattern; and an arteriosclerotic shape of the arterial wave was seen in men with short episode and flat trace patterns. Each erection period immediately after prostaglandin E1 injection in men with dissociation, short episode, low amplitude and flat trace was shorter compared with cases with a normal pattern. Venoocclusive dysfunction was observed in 5 men with a dissociation pattern and 6 men with a flat trace pattern. In conclusion, an integral analysis of pattern of NPT with rigidity and other examinations are useful for differentiating organic impotence from psychogenic impotence and for accurately diagnosing pathophysiological disorders of organic impotence and underlying diseases.