We report a four year follow-up of 39 of 47 infants born after pre-labour Caesarean section and 68 of 79 born vaginally. Loss of motor function due to late complications was more frequent in the Caesarean section group (Fisher's Exact; P = 0.004). However, the means of the differences between the X-ray levels (measured as the last intact vertebral arch seen on standard anteroposterior roentgenograms of the spinal column) subtracted from the motor levels still favour Caesarean section (mean = 3.24; SD = 2.7) over vaginal delivery (mean = 1.2; SD = 2.7) (Student's t-test; P = 0.0003). The frequencies of other complications, death and neonatal meningitis, were not significantly different. Another 38 infants born by Caesarean section after labour were more paralysed (mean of X-ray and motor difference = 1.8, SD = 2.2) following rupture of amniotic membranes than those with intact amniotic membranes with or without labour (mean = 3.4; SD = 2.2) (Student's t-test; P = 0.0067). The differences between X-ray and motor levels for patients born by Caesarean section with intact amniotic membranes and without labour (mean = 3.6; SD = 2.4) were not significantly different from those with labour and intact amniotic membranes (mean = 2.89; SD = 1.5). The number of new cases of meningomyelocele presenting to our clinic has decreased from an average of 30 per year between 1970 and 1987 to 14 between 1988 and 1992.