The Tana River Primate National Reserve, Kenya (TRPNR) yellow baboons' (Papio cynocephalus) long-term habitat usage and food preferences are relatively under-reported. The author presents a preliminary food catalog and analyses of 5 years of data (January 88–October 92; n=55 mo; 875 observation days; 4,893 hourly scans) for the Mchelelo troop (x̄=75 individuals). The author predicted that the TRPNR baboons would spend more time on the much larger savanna, show a seasonal preference for fruits/seeds, and show rainfall-influenced food preferences. Although more time was spent on the proportionately larger savanna than in the forests, more than 42% of the observations occurred in forests that accounted for only 8.7% of the area regularly used by the baboons. Fruits/seeds consumption was high throughout the period and a significantly higher proportion of each month's observations reflected fruits/seeds rather than grasses/herbs/corms consumption. Two forest species' (Phoenix reclinata and Hyphaene compressa) were particularly important. Regression analysis showed fruits/seeds consumption predicted most of the grasses/herbs/corms consumption variance. There was no statistical difference in rainy vs. non-rainy season fruits/seeds or grasses/herbs/corms consumption. One implication of these data is the baboons' potential impact on the critically endangered Tana River mangabeys (Cercocebus galeritus), which also rely heavily on P. reclinata and H. compressa. Another is what the “savanna” designation may or may not tell us about baboons. Am. J. Primatol. 71:432–436, 2009. © 2009 Wiley-Liss, Inc.