A survey of 612 black rats, Rattus rattus (282 males and 330 females), for infections with helminth parasites was carried out in Abeokuta, in southwest Nigeria. Three hundred and ninety six (64.7%) were infected with one or more of seven species of helminths comprising three cestodes (Hymenolepis diminuta, Taenia taeniaeformis (cyst) and Raillietina sp.) three nematodes (Mastophorus muris, Trichuris muris and Syphacia sp.) and one acanthocephalan (Moniliformis moniliformis). Although the prevalence of infection in males (76.6%) was more than in females (54.5%) (P< 0.01), there was no difference in the mean intensity of infection, MI, (males = 11.6 ± 0.94, females = 11.1 ± 1.56). Among the different weight classes, rats of 100–130g were more infected (89.3%) and had the highest mean intensity (MI = 21.6) than those that weighed <100g (47.1%, MI = 6.4) and >130g (73.9%, MI = 9.3). Moniliformis moniliformis was the most common species encountered (39.2%) and had the highest mean intensity in both sexes ( = 7.4 ± 0.74). Considering the rat-man proximity, this finding has considerable public health implications.