Persistent parainfluenza virus shedding in healthy young adults occurred throughout the 8½-month winter isolation period at Amundsen–Scott South Pole Station during 1978. Two episodes of respiratory illness were observed after 10 and 29 weeks of complete social isolation. Throat swabs collected both routinely, and during each outbreak of respiratory illness, were directly inoculated into cell cultures. Parainfluenza virus types 1 and 3 were recovered from both symptomatic and asymptomatic subjects throughout the winter. No other viruses were obtained by these efforts. The presence of parainfluenza virus in these subjects long after the accepted incubation period for viral upper respiratory illness, and when the introduction of new virus to this community was impossible, suggests its persistence in man.