BACKGROUND: Although childhood blindness is relatively rare, it is the leading cause of blind person years besides cataract. The aim of this study is to estimate the prevalence and causes of childhood blindness and severe visual impairment (BL/SVI) in southeast China. METHODS: The study took place across four administrative units in Xiu'shui County. Sixty key informants were trained by an ophthalmologist to identify possible cases of childhood BL/SVI (children < 16 years with presenting visual acuity < 6/60 in the better eye) in their own communities. The possible cases were referred to a hospital for further examination by a pediatric ophthalmologist, to ascertain case status and determine the cause of BL/SVI. RESULTS: In total we found 8 cases of childhood BL/SVI from a total population of approximately 27,000 children. The prevalence of childhood BL/SVI was therefore 0.3/1000 (95% Confidence Interval [CI]: 0.1-0.5/1000). The prevalence of blindness (< 3/60) was 0.2/1000 (95% CI: 0.04/1000-0.4/1000) and the prevalence of SVI (< 6/60-3/60) was 0.07/1000 (95% CI: 0-0.17/1000). The main cause of BL/SVI was posterior segment disease (87.5%). Half of the cases were potentially treatable. CONCLUSIONS: The study has documented a low prevalence of childhood BL/SVI in southeast China. Despite the low prevalence, half of the cases were potentially treatable if earlier medical action was taken, suggesting the prevalence could be reduced further still. The Key Informant Method is simple to implement and an efficient method for case finding in China.