The incidence of bronchopulmonary dysplasia (BPD) and neuro-developmental sequelae in 135 infants surviving intermittent positive pressure ventilation (IPPV) in the newborn period were studied in relation to primary disorders requiring IPPV. The rate of BPD increased over the 6-year study period in hyaline membrane disease survivors from 14% to 28%, but decreased in infants with apnoea repetens from 38% to 13%. Immaturity seemed to be one important factor for development of BPD. The incidence of neuro-developmental sequelae in IPPV treated infants fell from 22% to 13% over the years. In infants with birth weight below 1501 g the rate of neurological handicaps was 11%.