1. This paper presents body mass and population density data for 88 African forest mammal species from over 200 references. It uses phylogenetic comparative methods to examine the association between population density and body mass in relation to diet both in these data and in a similar compilation of data from over a hundred neotropical forest mammal species. 2. Predictably, population densities declined with increasing body mass. The regression slope of log density on log mass for all the data combined was -0.54 (SE 0.075). 3. Density decreased with increasing trophic level and with increasing specialization, although these factors could not be separated. The slope of density on mass did not differ significantly among trophic levels nor among dietary categories. Myrmecophagy, the most specialized diet, seemed to be associated with the lowest relative population densities. 4. The slopes obtained for the African assemblage and for all data combined were significantly different from -0.75. Within dietary categories and within trophic levels, slopes did not differ significantly from -0.75, although sample sizes were often small. 5. There is no evidence to suggest that the relationships between mass, density and trophic level differ between Afrotropical and neotropical forest mammals.