Several states, of whom France, have been alarmed about suicide in the military. An observational longitudinal cohort study was conducted to check whether the suicide risk in the French army was higher than in the general population and to find out the more prone to self-harm destruction personnel categories. From 1997 to 2000 inclusive, 230 suicides occurred among 315,934 person.years; i.e., the overall annual crude suicide rate was 18.2 per 100,000 active-duty personnel. With the National data for 1999 as reference, army men had a lower suicide risk than men in the overall population of similar age categories (standardised mortality ratio = 67). A Poisson regression model showed that the incidence rate in the Gendarmerie was twice as high as in the Land Forces (incidence rate ratio = 2.15), that the incidence relative risk increased threefold over 4 years, and that the incidence rate ratio amongst under 25 and from 40 to 44-year-old personnel was almost twice as high as in the 25-29-year-old category. The main suicide methods were use of a firearm (51%) and hanging (28%). Despite a global lower risk than in the general population, certain army categories, i.e., Gendarmerie personnel and young men, deserve specific surveillance and preventive measures.