BACKGROUND: In northern Nigeria, trachoma is an important public health problem, but there are currently few population-based data on prevalence of disease and no formal trachoma control programs. METHODOLOGY/PRINCIPAL FINDINGS: In Kano state, Nigeria, we conducted a population-based cross-sectional survey using multistage cluster random sampling, combining examination for clinical signs of trachoma and application of questionnaires assessing potential household-level risk factors. A total of 4491 people were examined in 40 clusters, of whom 1572 were aged 1-9 years, and 2407 (53.6%) were female. In 1-9 year-olds, the prevalence of trachomatous inflammation-follicular (TF) was 17.5% (95% CI: 15.7-19.5%). In a multivariate model, independent risk factors for active trachoma were the presence of flies on the face (OR 1.98, 95% CI 1.30-3.02); a dirty face (OR 2.45, 95% CI 1.85-3.25) and presence of animal dung within the compound of residence (OR 3.46, 95% CI 1.62-7.41). The prevalence of trachomatous trichiasis in persons aged ≥15 years was 10.9% (95% CI: 9.7-12.2%). Trichiasis was significantly more common in adult females than in adult males. CONCLUSION/SIGNIFICANCE: There is an urgent need for a trachoma control program in Kano state, with emphasis given to provision of good quality trichiasis surgery. Particular effort will need to be made to identify women with trichiasis and engage them with appropriate services while also taking steps to secure azithromycin for mass treatment and ensuring personal and environmental hygiene.