Aim of the study is to verify if a stress reaction due to G8 meeting, held in Genoa on July 2001, can produce a mass stress reaction and influence negatively people sexuality and so the birth rate. 402 citizens (221 men and 181 women ranging in age from 25 to 52 years, mean 39) have been invited to answer two questionnaires concerning their sexual activity and their feelings before, during and after the G8 meeting. After 9,10 and 11 months we have valued the birth rate in Genoa. 30 people (7%) did not answer the two questionnaires. 12 people (3%) answered the questionnaire wrongly and were excluded from the study. 228 people (63%) didn't report changes about their sexual activity, during G8 meeting. 120 people (33%) reported a decrease of sexual intercourses and of sexual desire; 12 people (4%) reported an increase of these parameters. 54% of our population reported a definite anxiety. We want to emphasize the high number of people that had anxiety even in the group that didn't report changes in sexual activity (105/228 = 46%). After 9, 10 and 11 months we have recorded a significant decrease of the birth rate respectively of 29%, 23%, 20%. (P < 0.05). Violent demonstrations during G8 meeting have negatively influenced people sexual activity and people behaviour. Besides, we have recorded a decrease of birth rate in Genoa, nine, ten and eleven months after G8. This decrease rate was respectively 29%-23%-20% as regards the same months during the three years before (P < 0.05). We cannot determine the real cause of this decrease. Violent G8 demonstrations could be responsible for a stress reaction with negative consequences on human reproductive functions.