Perinatal mortality rates were determined for all public maternity hospitals in New Zealand for the years 1978-1981. Level 1 maternity hospitals-mostly small rural units staffed by general practitioners and midwives-had lower birth-weight-specific perinatal mortality rates in all but the lowest birth-weight categories than the better equipped hospitals to which they refer. This probably reflects the cautious antenatal practices of general practitioners, and the effective regionalisation of perinatal services in New Zealand. It is also possible that there is an advantage, particularly for normal birth-weight children, in being born in smaller obstetric units. There is no evidence that a satisfactory outcome depends on a minimum number of deliveries.