Abstract: Abstract:The method and the criteria of the nocturnal penile tumescence test (NPT) were reviewed. Their problems in the practice of dimeal forensic medicine were discussed. We recomend that all the patients must undergo a NPT test for 3 consecutive nights by means of Rigiscan device and a record will be considered normal when the rigidity of erection is greater than 70% at the tip and base of the penis with a minimum duration of 100 miniuters.