​The prevalence of Du phenotype was investigated among rhesus negative women of childbearing age (15–45 years) in Port Harcourt, Nigeria, over a period of 17 months. A total of 1,108 women were randomly sampled, out of which 1,003 (90.5%) were rhesus positive and 105 (9.5%) rhesus negative. Only one (0.95%) of the Rh-negative women was Du positive while 104 (99.05%) were Du negative (true rhesus negatives). The results show that the incidence of Duphenotype in Nigeria may not be uniform — it is high among the Yorubas (7.5%) and rare among the Ijaws and Efik-Ibibios of the south-east. The results also suggest that Du testing may not be indicated in all individuals initially typed as rhesus negative while being strongly indicated only in areas of high prevalence. More studies are required in other parts of Nigeria to provide data that may facilitate the adoption of a comprehensive nationwide policy on appropriate management of rhesus negative women in the country.