The results of surveys among 188 primary school children in two hyperendemic rain-forest villages in South-West Cameroon are reported. The children were examined for their nutritional state and for lesions due to onchocerciasis, with emphasis on eye pathology. Clinical manifestations in the two villages hyperendemic for onchocerciasis were compared with those found in a hypo-endemic coastal village. The primary school age appeared to be the period with the highest increase in ocular, notably corneal, involvement in onchocerciasis. The prevalence of ocular involvement showed an increase from 42.8% in the 6-year age group to 100% in the 12-year age group. 17.5% of the children were considered to be at risk of developing serious ocular onchocerciasis. Significant correlation between nutritional state and severity of infection could not be demonstrated. Sex differences in onchocercal symptomatology appeared not to be significant. The importance of microfilarial concentration in the skin snip near the eye is stressed as a simple but important indicator of danger to the eye. Prognosis and therapy are discussed.