OBJECTIVE The objectives of this study were to determine the prevalence and pattern of stimulant use and its association with 'brain fag syndrome' among secondary school students in Osogbo, Osun State. The study also aimed to determine the association of socio-demographic variables (of the students and their parents) with stimulant use. METHODS A questionnaire consisting of sociodemographic variables, the stimulant use section of the WHO Student Drug Use Questionnaire and the Brain Fag Syndrome Scale (BFSS) was administered on randomly selected students of the two Local Government Areas of Osogbo. The prevalence rates of stimulant use were calculated and the association of stimulant use with Brain Fag Syndrome (BFS) and socio-demographic variables was determined. RESULTS The 30-day prevalence rate of stimulant use was 20.3%. Users engaged more in the use of common and cheap stimulants (coffee and kola nut). Majority of users started at age 13 years or below. There was a very high relationship between stimulant use and the symptoms of the BFS (p<0.001). Stimulant use was associated with lower age group, poor school attendance, polygamous background, low education of mother, high education of father and the description of mother as being too permissive. CONCLUSIONS The findings suggest the need to increase the awareness of the dangers of stimulant use among students. Control programmes are urgently needed to prevent student wastage.