The aim of this investigation was to study the contemporary pattern of perinatally acquired brachial plexus palsy (BPP) in Sweden. National incidence data were collected from the Swedish Medical Birth Registry. The clinical pattern of BPP was studied in the county of Skaraborg. All children (n = 52) with confirmed neonatal BPP in 1981-89 were assessed 4-14 y after birth using routine neonatal and follow-up documentation for retrospective analysis and an assessment battery for the clinical evaluation of impairment. The mothers' recollection of the birth process was recorded by interview and compared with two control groups. The incidence of BPP in Sweden increased significantly from 1.4 per mill in 1980 to 2.3 per mill in 1994. The incidence was 45 times higher at a birthweight of > 4500 g than at a birthweight of