Intentional violence consists mainly of non-accidental interpersonal violence and suicidal behaviour; the remaining categories are other violence and/or violence with undeterminted intention [corrected]. In almost all the countries considered in this study, intentional violence is taking on worrying proportions in adolescence (10-19-year-olds) and is on the increase among young adults (15-24-year-olds). The scale of the problem is relatively well known thanks to national mortality rates. The relative proportions of murders and suicides vary considerably from one country to another, though they remain fairly constant over time, whether the diachronic progression of mortality due to intentional violence increases, remains stable or falls in the country concerned; this is true for both sexes and for both the age groups considered (15-19 and 20-24). Nevertheless, in view of the much higher incidence of intentionally violent behaviour that does not result in death, more resources should be allocated to epidemiological studies in that area, especially in terms of quantitative and qualitative methods, where possible in association with interdisciplinary projects. Only with a better knowledge of the risk factors and if possible identification of the predictive factors (in the probabilistic sense of the term) could we devise, conduct and evaluate preventive measures that are better targeted than those used so far, whether the factors are socio-cultural, socioeconomic or psychosocial. This is the justification, especially the ethical justification, of further epidemiological studies of an analytical or even interventional nature, going beyond the descriptive studies that have been made by most researchers to date.