During the latter half of 1961, six hundred and thirty-one small mammals (mainly insectivores and rodents), representing approximately fifty species, were trapped in various types of vegetation in Uganda. These included grassland, scrub, palm forest, moist evergreen forest, moist montane forest, bamboo forest and sedge swamp in west and central Uganda as well as dry, tree savanna in the north-east. Most habitats contained a large number of species wdh appreciable diversity occurring between habitats. Several of the species caught in comparatively large numbers, e.g. Praornys, Hylomyscus, Lemniscomys striatus, Mastoniys and Arvicanthis, showed little reproductive activity. Other species were more active. The reasons for these differences have been discussed. A small amount of information is given on the activity of animals at different times of the day.