Biopsy samples from 20 patients with a history of laryngeal papillomas were analyzed by Southern blot hybridization for the presence of human papillomavirus DNA. All papillomas examined contained papillomavirus DNA sequences. Four samples from uninvolved sites in two patients with active disease and eight samples from patients in remission also contained viral DNA. No human papillomavirus DNA was detected in a third patient seen during remission. These results explain the clinical pattern of frequent recurrences even after long-term remission in laryngeal papillomatosis.