Studing 40 women of one prison, the author found that the incidence of premenstrual tension syndrome was 35% of the group. Among the crimes of known distribution, 40% occurred in the first week before the menstrual flow. At that time, occurred 45.4% of all thefts, 47.3% of all violent crimes and 53.8% of the murders. Twenty per cent of the crimes occurred during the menstrual flow. It has been verified that the absence of premenstrual tension syndrome does not signifies less chances of occurring crimes during the week prior to the flow.