The primate genus Theropithecus is represented at various Plio-Pleistocene sites including the Pliocene site of Makapansgat (2.9 mya), the early Pleistocene cave of Swartkrans (1.8 mya), the late Pleistocene deposits from Elandsfontein (700,000 ka) and by extant gelada baboons from Ethiopia. To examine how diet has changed over time in this genus, dental microwear features of Theropithecus darti (n=2), Theropithecus danieli (n=8), Theropithecus gelada (n=2) Theropithecus oswaldi (n=1) Parapapio whitei (n=14), Papio robinsoni (n=16) and Papio ursinus (n=13) were examined under low-magnification (35x) using light refractive technology. Although there is a significant relationship between small pits and fine scratches, Analysis of Variance followed by Tukey’s post-hoc tests failed to demonstrate significant groupings. However, bivariate analyses suggest that as scratch count increases, pit count decreases. The results suggest that there is much dietary variation in modern and extinct gelada baboons, but that extant Theropithecus relies somewhat more on grassland resources than did their extinct counterparts.