One hundred forty-seven (66%) of 224 scouts and chaperons were interviewed after a weekend visit to a dude ranch in upstate New York. One hundred seventeen (80%) complained of papular rashes or eye and ear inflammation. Onset of illness occurred within 24 to 48 hours of arrival at the ranch. After controlling for participation in other available activities, only swimming was found to be associated with illness. Pseudomonas aeruginosa serotype 0 11 grew from a culture of pool water and from 17 cultures of skin, eye, and ear lesions in visitors to the ranch. Follow-up was obtained for 76 of the affected persons for whom initial information was available. Mean duration of illness was 14.5 days (range, one to 40+ days). The recurrence rate was 24%.