In a study of 30 children with uncomplicated respiratory syncytial virus (RSV) pneumonias, a high incidence of lobar collapse (8/30-26%) was noted. This involved the right upper lobe in seven patients and the left upper lobe in one patient. It is probably attributable to anatomical predispositions, sloughing of necrotic epithelium, and stimulation of mucus production. Lobar collapse should be considered part of the spectrum of RSV pneumonitis.