The status and distribution of eastern African populations currently assigned to Hylomyscus denniae are reviewed based on morphological and morphometric comparisons. Three species are considered valid, each confined largely to wet montane forest above 2000 meters: H. denniae (Thomas, 1906) proper from the Ruwenzori Mountains in the northern Albertine Rift (west-central Uganda and contiguous D. R. Congo); H. vulcanorum Lönnberg & Gyldenstolpe, 1925 from mountains in the central Albertine Rift (southwestern Uganda, easternmost D. R. Congo, Rwanda, and Burundi); and H. endorobae (Heller, 1910) from mountains bounding the Gregory Rift Valley (west-central Kenya). Although endorobae has been interpreted as a small form of Praomys, additional data are presented that reinforce its membership within Hylomyscus and that clarify the status of Hylomyscus and Praomys as distinct genus-group taxa. The 12 species of Hylomyscus now currently recognized are provisionally arranged in six species groups (H. aeta, H. alleni, H. anselli, H. baeri, H. denniae, H. parvus) based on 8 qualitatitive characters. Biogeography of the three species of the H. denniae group is discussed in the context of broad distributional patterns and area relationships evident among other terrestrial small mammals also confined to the Afromontane biotic region in eastern Africa.