Five, 1-week-old, colostrum-deprived lambs were inoculated transtracheally with a parainfluenza type-3 (PI-3) virus that had been isolated from a pneumonic lamb lung. A biphasic febrile response, cough, rapid breathing followed by forced expirations, listlessness, and anorexia were observed in the lambs. There were multifocal areas of consolidation in the lungs of all lambs and ulcerations in the nasal mucosa of three lambs. Serum antibody titers to PI-3 virus ranged from 2 to 16 in lambs necropsied Day 3 to Day 7 post-inoculation, respectively. Virus was isolated from nasal secretions, tracheal fluids, and lung tissues of all lambs.