A rubella epidemic occurred on St. Paul Island, Alaska, in 1963, after an absence of 22 years. It spread rapidly through the community of 400 inhabitants and virtually disappeared in less than two months. Antibodies developed in 90% of those serologically susceptible. Rash appeared in 40% to 90% of susceptibles, with the highest rates among 15- to 19-year-olds. Rubella virus was recovered as much as 13 days before rash and six days after rash. Antibody was first detected the day after appearance of rash. Among susceptibles who did not develop rash, the majority had characteristic lymphadenopathy, and rubella virus could be recovered from the throat for up to four days. There were no patients with rash among those over 22 years of age, 90% of whom had preexisting antibody.