Suicide is a great problem for public health. In France it causes more than 12,000 deaths every year, and it has been estimated that 45 to 70% of these subjects were suffering of affective disorders. Some epidemiological aspects of the links between suicide and depression are analytic and concern the risk factors of suicide among depressed patients: sociodemographic factors: risks are more important for men and for people living alone or suffering of social and affective isolation. Violent suicides increase with age; clinical and evolutive characteristics of the illness: the risk of suicide is correlated with the global severity of the depression, whatever are the nosographic subtypes, with anxiety, sleep disorders and anhedonia, with personal and familial history of suicide; among biological factors, a decrease of 5-HT transmissions has been implicated, but it seems to be more correlated with a modification of the ability to delay, with a poor impulse control. The association of several of these factors increases suicidal risk but it is impossible to describe a specific picture of the depressed suicidal patient, and clinical scales to estimate suicide risk are of limited interest. Finally, the clinical vigilance adapted to each individual case and the quality of the therapeutical relation remain the most important point for preventing suicide.