The samango monkey (Cercopithecus mitis erythrarchus Peters, 1852) is the southernmost representative of the widely-distributed polytypic Cercopithecus mitis species-group. At Cape Vidal (28d̀ S) climatic seasonality causes significant seasonal fluctutation in food abundance. There are, however, no congeneric competitors, and few arboreal frugivores (birds, bats). In spite of seasonality of food abundance at Cape Vidal, samango monkeys maintain a high quality diet, dominated by fruit (51.7%), throughout the year. To a large extent this is made possible by their broad dietary tolerances and the effect of competitive release on food choice. Seasonal insect abundance does, however, place serious constraints on the availability of readily-digestible protein and the acquisition of protein-rich foods must be seen as the critically limiting factor in the dietary behaviour of the samango monkey. Adaptation of gut morphology and symbiotic microflora permit samangos to supplement the diet with large amounts of protein-rich foliar and floral items. Where necessary, even large quantities of less palatable items, such as unripe fruits and mature leaves, may be ingested. Although insects form a small part of the diet a larger variety, than used by equatorial C. mitis populations, are included in the diet. Given that there are no congeneric competitors, nor are the monkeys particularly food stressed, I suggest that the diet of the samango monkey at Cape Vidal most closely reflects the intrinsic food choices of the C. mitis species-group.