Within the Great Lakes of Africa exist the world's most diverse communities of freshwater fishes (Fryer and Iles 1972, Greenwood 1974, Ribbink et al. 1983). In particular, the nearshore waters of Lakes Malawi and Tanganyika contain flocks of species, mostly members of the family Cichlidae, which may attain densities of up to 22 species and >500 individuals in a 50-M2 area (Ribbink et al. 1983). While many of these cichlid species are very similar in general body morphology, is high interspecific diversity in neurocranial morphology and dentition (Fryer and Iles 1972, Reinthal 1990a). This morphological diversity suggests that interspecific differences in feeding strategies may play an important role in reducing interspecific competition and maintaining high species diversity (Fryer and Iles 1972, Reinthal 1990a). Yet the results of studies investigating feeding habits of cichlids have been equivocal. Initial studies of the stomach contents of rock-dwelling fishes (Fryer 1959, Ribbink et al. 1983) showed little or no evidence of food partitioning. This, along with laboratory studies (Liem 1984), suggested that herbivorous cichlids, while being facultative specialists, are generally nondiscriminatory feeders. In reviewing the available literature on cichlid feeding habits, Greenwood (1981:71) concluded that there is apparently complete interspecific overlap in environmental requirement. If this is true, then partitioning may occur only during periods of low food supply (McKaye and Marsh 1983). More recent research (Van Oijen 1982, Reinthal 1990b) has found significant variation of stomach contents among cichlid species. However, because stomach contents represent food consumed over a small time period and within a small area, these results do not conclusively demonstrate whether food partitioning is the exception or the rule. Other disadvantages of stomach content analyses include difficulty of identification and uncertainty over whether all observed stomach contents are assimilated to the same degree, or if some components, such as cyanobacteria, are indigestible (Fryer 1959, Ribbink et al. 1983, Reinthal 1990b). In this note we present evidence for food resource partitioning among fishes of Lake Malawi, Africa, by comparing the stable isotope composition (b13C and b15N) of a number of nearshore fish species and their potential food sources. Because a fish's isotopic composition represents a spatio-temporal integration of the composition of assimilated food, this approach circumvents many of the problems in stomach analyses noted above.