During the two last decades, several epidemiological studies have been conducted on bulimia nervosa. According to recent studies, prevalence rates were estimated to be 1%. There are a very few studies on eating behaviour conducted in Arab countries. The aims of the current study were to assess prospectively the prevalence of Bulimia Nervosa and its characteristics in a Moroccan context in a randomly selected and representative sample of students attending six secondary schools in Casablanca. A second group composed of the students of the French secondary school of Casablanca was included in the survey in order to verify the influence of socio-cultural factors. Subjects completed a sociodemographic questionnaire and the Bulimic Investigatory Test of Edinburgh (BITE), a 33-item self-report measure of both the symptoms and severity of bulimia nervosa. A score of 25 or higher suggests a bulimic syndrome; 2,044 subjects returned their questionnaires (participation rate = 75.8%). The group of Moroccan school included 1,887 subjects and the French school 157 subjects. Females were preponderant (59%). The mean age was 18.3 +/- 1.2 years (15-22 years). For the first group, at least one substance was taken by 290 (15.3%) students: 12.7% were addicted to tobacco and 5.7% consumed occasionally alcohol. 16.3% reported a familial history of disturbed eating behaviour. According to the BITE, the overall prevalence of bulimia was 0.8% (1.2% in female and 0.1 in male subjects). The mean age of bulimic subjects was 18.6 +/- 1.7 years (16-24 years). The only male case in our sample was aged 24 years, without personal nor familial psychiatric history, consumed regularly tobacco and alcohol. His BITE symptoms score was 20 and severity score was 17, the highest score in our sample. Analyses of correlates of bulimia nervosa in the Moroccan sample showed that the group of bulimic subjects did not differ from the non bulimic with regard to any sociodemographic characteristics except sex: the female sex was predominant (p < 0.005) with 14 cases, the prevalence of bulimic syndrome was 1.2% among girls. This prevalence was 0.1% among boys. The bulimic subjects have regularly used different compensatory behaviours to control their weight: 6 (33.3%) used appetite suppressants, 3 (16.6%) used diuretics and 4 (22.2%) were engaged in self-induced vomiting. In the group of the french school, the prevalence of bulimia was 1.9% in the whole sample (3.4% among girls and no case among boys). These results are comparable to those reported recently in occidental countries and in an Egyptian study. However, the prevalence of bulimic syndrome in our sample was lower to those reported in countries with similar culture. The elevated prevalence of 10% reported in a tunisian study could be explained by the composition of the sample (medical students, aged 22-28 years) and the cut-off point for the BITE was determined to be 20 without taking into account severity criteria. A South African survey, conducted on 1,435 college students representing South Africa's ethnically and culturally diverse population comparable to our sample regarding the age (17-25 years), found a prevalence of 5% with a cut-off of 25 in the BITE. The majority of epidemiological community-based studies estimated the prevalence of bulimia nervosa to be 1 to 3% according to the diagnostic instruments used (self-report questionnaires versus clinical interviews) and the diagnostic criterias operationalized (DSM III, III-R or IV). The rate of occurrence of this disorder in males usually one-tenth of that in females was more decreased among our sample. However, the prevalence among males was comparable to the data of literature. Except the sex, we did not find other risk factors identified in the previous papers. Although in the bulimic group, we noted a higher rate of substance abuse (26.6% versus 15.2%, p > 0.5), familial histories of disturbed eating behaviour (26.6% versus 16.2%, p > 0.3) and less regular practice of sportive activity (72.2% versus 92.3%, p > 0.1), these differences are not statistically significant. The review of the literature identified at least 5 domains associated to bulimic disorder: parental problems (lower parental contact or separation, disruptive events), vulnerability to obesity, parental psychiatric disorder (alcoholism, depression), sexual or physical abuse and a premorbid psychiatric disorder. With the enormous media coverage and the globalisation of the media, cultural differences are disappearing. In order to estimate the prevalence of bulimia nervosa in the Moroccan population and to identify the risk factors, further epidemiological community-based studies using structured psychiatric interviews are required.