A comprehensive survey of onchocerciasis was performed on 1259 inhabitants in San Vicente Pacaya and the surrounding area. The total number of inhabitants examined was 1259, 763 males and 496 females. An examination of microfilarial density was carried out by the skin snip method. There were 610 microfilarial positives (50.4%) out of 1211 persons, 448 males (60.9%), and 162 females (34.1%). Nodules were examined by palpation, and there were 404 (32.8%) positives for nodule out of 1232 persons, 299 males (40.3%), and 105 females (21.4%). Eczematous dermatitis was seen in 149 persons, the generalized type in 13, and other types in 136. Depigmentation on the lower extremities was seen in 290 persons, the severity was graded from 0 to 4, and grade 1 depigmentation was seen in 91; grade 2, in 143; grade 3, in 52 and grade 4 in 4 persons out of 1159 individuals examined. The positives for lymphadenopathy (above grade 2) were 464 (41.2%) out of 1127 individuals. Itching was seen in 129 (18.3%) of 705 individuals examined by the inquiry card method. The correlation between skin changes and onchocerciasis was also analyzed. Those individuals who were microfilarial positive in the skin snip and eyes, and who had palpable nodules were defined as being onchocerciasis patients. There was a high frequency of eczematous dermatitis, depigmentation on the lower extremities and lymphadenopathy in the onchocerciasis infected group, compared with the non-infected group, but there was no difference in the rate of itching between them. Hanging groin, elephantiasis and "erisipela de la costa" were not seen in this endemic area, and the degree of skin changes was slight, compared with that reported in Africa thus far.