The prevalence of Plasmodium falciparum parasitaemia was evaluated in 59 neonates admitted to the University College Hospital, Ibadan in South-western Nigeria between August and December 1991-a period spanning part of both wet and dry seasons. Peripheral parasitaemia was present in 14 (23.7%) neonates; of these, four were preterm (4/26, 15%) and ten were term babies (10/33, 30.3%). The difference in the prevalence of P. falciparum parasitaemia in the two groups was not statistically significant (chi2 = 1. 78; p = 0.10). Parasite densities in all neonates were uniformly low (< 2000 asexual forms/mul blood), and only four of the neonates had fever within 48 hrs of birth. Infected neonates weighed 200 g more than non-infected neonates, but the difference was not statistically significant. Maternal weekly pyrimethamine prophylaxis did not appear to be effective in preventing infection as six (21.4%) of the 28 neonates whose mothers had regular prophylaxis had parasitaemia compared with seven (26.9%) of the 26 neonates whose mothers had no prophylaxis (chi2 = 0.22; p > 0.05). These data indicate that congenital malaria is not as uncommon as was previously thought and that the recent increase in reported cases may be due to an interplay of several factors.