Acute hemorrhagic conjunctivitis has caused numerous outbreaks throughout Africa and Asia since it was first recognized in 1969 but did not involve the New World until 1981. This unprecedented outbreak reached Colon, Panama during August 1981 and by October 8,401 cases had been reported (14% of Colon's population). In October the Gorgas Memorial Laboratory and Ministry of Health conducted a survey in Colon to collect descriptive data on household living units, epidemiologic and clinical data from residents, and venous blood from all residents one year or older. The survey sampled 127 households and interviewed 608 people (1% of Colon's homes and 1% of the population). Overall 336 (55%) study subjects recalled having conjunctivitis. Disease rates differed according to residence; poor sectors of the city had 67% attack rates, lower class 52%, middle class 34%, and upper class 13%. Within each sector adults were more likely than children to be index cases, and communal bathrooms and household crowding were the most important risk factors for acute hemorrhagic conjunctivitis. Between 4–20% of people denying acute conjunctivitis had antibody to enterovirus 70 and may represent asymptomatic cases.