Objective: To examine associations between exposure to physical violence (PV) or sexual violence (SV) and adverse health behaviours among a sample of children in five African countries. Methods: In a cross-sectional analysis of data from Namibia, Swaziland, Uganda, Zambia and Zimbabwe - countries that participated in the Global School-based Student Health Survey in 2003 or 2004 - we compared the relative frequency of several adverse health behaviours among children (primarily students 13-15 years of age) who did and who did not report exposure to PV or SV. We estimated odds ratios (ORs) for such behaviours and their 95% confidence intervals (CIs) after adjusting for age and sex. Findings: Exposure to PV during the 12 months preceding the survey was reported by 27-50% (average: 42%) of the children studied in the five countries, and lifetime exposure to SV was reported by 9-33% (average: 23%). Moderate to strong associations were observed between exposure to PV or SV and measures of mental health, suicidal ideation, current cigarette use, current alcohol use, lifetime drug use, multiple sex partners and a history of sexually transmitted infection (P ≤ 0.05 for all associations). For example, the odds of being a current cigarette smoker were higher in children involved in one fight (OR: 2.20; 95% CI: 1.77-2.75), 2-5 fights (OR: 3.43; 95% CI: 2.54-4.63), or 6 fights or more (OR: 5.95; 95% CI: 4.37-8.11) (P for trend < 0.001) during the 12 months preceding the survey than in children unexposed to PV. Conclusion: Childhood exposure to PV and SV is common among African children in some countries and is associated with multiple adverse health behaviours. In developing countries, increased awareness of the frequency of exposure to violence among children and its potential health consequences may lead to heightened attention to the need for health promotion and preventive programmes that address the problem.