In Switzerland, data are collected prospectively by collaborators from all nine neonatal intensive care units and their affiliated paediatric units caring for neonates, to determine su rvival and (pulmonary) outcome of infants with birth weights ranging from 501 to 1500 g. To assess the pulmonary outcome of very low birth weight (VLBW) infants in Switzerland in 1996 and 2000, factors associated with bronchopulmonary dyspl asia (BPD) were identified and compared with pulmonary outcomes from the Vermont Oxford Network data. BPD was defined as a requirement for supplemental oxygen a t 36 weeks postmenstrual age. Complete data were available for 600 and 636 VLBW infants in 1996 and in 2000, respectively. Mortality rates in Switzerland were s ignificantly higher (1996: 19.2%, 2000: 20.8%) than in the Vermont Oxford Netw ork (1996: 14%, 2000: 14%). Expressed as percentage of infants still hospitali sed at 36 weeks postmenstrual age, 16.7%and 13.2%of Swiss VLBW infants were di agnosed with BPD in 1996 and 2000, respectively. These rates were significantly lower than in the Vermont Oxford Network (1996: 28%, 2000: 35%). Infants expos ed to factors previously shown to be associated with BPD were investigated: in S witzerland, infants with a history of surfactant replacement therapy and/or mech anical ventilation had a significantly higher rate of BPD in both cohorts. Infan ts with postnatal transport, sepsis proven by positive blood culture and patent ductus arteriosus had a higher BPD rate only in the 1996 cohort. Between 1996 an d 2000, mortality rates and incidence of BPD in VLBW infants remained unchanged in Switzerland. BPD rates in Switzerland are lower than those found in the Vermo nt Oxford Network whereas a mortality rate comparison displays an inverted pictu re. We suspect that these effects are interrelated and may be due in part to a s elective approach of Swiss neonatologists to resuscitation of infants in the sma llest birthweight stratum. Conclusion:The factors listed above have apparently b ecome less important in the context of bronchopulmonary dysplasia and other infl uences, including prenatal conditions, will need to be investigated. In Switzerland, data are collected prospectively by collaborators from all nine neonatal intensive care units and their affiliated pediatric units caring for neonates, to determine su rvival and (pulmonary) outcome of infants with birth weights ranging from 501 to 1500 g. To assess the pulmonary outcome of very low birth weight (VLBW) infants in Switzerland in 1996 and 2000, factors associated with bronchopulmonary dyspl asia (BPD) were identified and compared with pulmonary outcomes from the Vermont Oxford Network data. BPD was defined as a requirement for supplemental oxygen at 36 weeks postmenstrual age. Complete data were available for 600 and 636 VLBW infants in 1996 and in 2000, respectively. Mortality rates in Switzerland were s ignificantly higher (1996: 19.2%, 2000: 20.8%) than in the Vermont Oxford Netw ork ( 1996: 14%, 2000: 14%). Expressed as percentage of infants still hospitali sed at 36 weeks postmenstrual age, 16.7% and 13.2% of Swiss VLBW infants were di agnosed with BP These rates were significantly lower than in the Vermont Oxford Network (1996: 28%, 2000: 35%). Infants exposed ed to factors previously shown to be associated with BPD were investigated: in S witzerland, infants with a history of surfactant replacement therapy and / or mech anical ventilation had a significantly higher rate of BPD in both cohorts. Infan ts with postnatal transport, sepsis proven by positive blood culture and patent ductus arteriosus had a higher BPD rate only in the 1996 cohort. Between 1996 and d 2000, mortality rates and incidence of BPD in VLBW infants remained unchanged in Switzerland. BPD rates in Switzerland are lower than those found in the Vermo nt Oxford Network an a mortality rate Comparison indicators an inverted pictu re. We suspect that these effects are interrelated and may be due in part to as elective approach of Swiss neonatologists to resuscitation of infants in the sma llest birthweight stratum. Conclusion: The factors listed above have apparently b ecome less important in the context of bronchopulmonary dysplasia and other infl uces, including prenatal conditions, will need to be investigated.