The aim of our study was to investigate the effect of perinatal asphyxia on developmental apoptosis in the cervical and lumbar spinal cord in the neonatal rat. Perinatal asphyxia was induced by keeping pups at term in utero in a water bath at 37 degrees C for 20 min, followed by resuscitation. Effects of this treatment on developmental apoptosis were studied on postnatal days 2, 5 and 8 using terminal deoxynucleotidyl transferase (TdT)-dUTP-biotin nick end labelling (TUNEL) and caspase-3 staining. TUNEL positive cells were identified using double immunostaining. On postnatal day 2 an increase of 215% in TUNEL positive cells was detected (P=0.005) in laminae IV-VII of the lumbar spinal cord of rats which underwent perinatal asphyxia compared to controls. An increase of 55% compared to controls (P=0.03) was seen in laminae I-III of the lumbar spinal cord at postnatal day 8. TUNEL positive cells could be partly identified as microglia cells (ED1 positive) and oligodendrocytes (O4 positive). The effect of perinatal asphyxia on programmed cell death in the neonatal rat spinal cord was mainly observed in the intermediate zone and dorsal horn of the lumbar spinal cord. We conclude that perinatal asphyxia has a pronounced effect on the survival of cells in a specific region of the spinal cord and thus may have a profound effect on the development of motor networks.