Mental disorders constitute an important portion of the world sickness ratio. In developing countries, in the absence of data on morbidity, hospital statistics are worthy of interest. Our study was carried out on a population of patients under care in the department of psychiatry of the Ouagadougou Hospital between January 1st 1990 and December 31st 2000, a period of 11 years. For each patient, we noted the sociodemographical features and the clinical diagnosis refering to the ICD-10 of the WHO. Within the scope of the study, 7 313 patients (60% men and 40 % women) were analysed. The average age of the patients was 31.06 ± 13.07 years. Among these patients, 80.60 % had been exclusively under ambulatory-care and 19.40 % had been hospitalized at least once. The main categories of the avai-lable diagnoses were listed according to recurrence : acute psychotic disorders (20.68 %), schizophrenia (17.25 %) and depression (15.13 %). In the men, the main diagnosis was acute psychotic disorders, whereas depression came top of the list for women. In the present state of socio-economic and cultural development in Burkina Faso, we note that only very serious mental disorders and/or those who cannot obtain favourable response with the traditional care system, come to medical centers. Therefore, there is a need to investigate the population as a whole, and to assess their need for medical care in this domain.