Primary or essential dysmenorrhoea is a painful syndrome which precedes by a few hours or accompanies the menstrual flow, present above all in adolescents. The aim of the present work is to evaluate the incidence of dysmenorrhoea in adolescents who practice sports. We examined two groups of athletes who practised sport in their adolescent period: 1) first population of athletes (483 subjects): women who had begun their activity before menarche (Group A: 261 subjects) and athletes who had started some years after the menarche (222 subjects); and in this latter group before (Group B1) and after (Group B2) the beginning of sports activity. 2) Second population (281 subjects) comprising: Group C (169 adolescents) comprised women who took part in sport only now and then; Group D (112 women) whose activity was of an athletic type. Comparing the percentage of dysmenorrhoea it emerges: 1) that dysmenorrhoea is present in a lower percentage in subjects in Group A (68.19%) in respect to women in Group B; 2) that in a considerable number of girls in Group B it was observed that there was a regression or an improvement in the pain symptomatology after the beginning in athletic activity; 3) dysmenorrhoea was much less in the more intense the sports activity (Groups C and D). From these data it can therefore be seen that athletic activity of almost any type or level has a positive influence on the dysmenorrhoea symptom, while it does not produce the same effect on other characteristics of the cycle, indeed, in some cases they were worsened.