Individual daytime activity patterns of gerenuks (Litocranius walleri) and giraffes (Giraffa camelopardalis) varied considerably, being influenced by such factors as the social environment, reproductive status, predators, and weather conditions. In male gerenuks and female giraffes, relative feeding time per day was inversely correlated with ambient temperature at 14.00 hours; the same relationship applied to mean distance moved per hour by female giraffes. Gerenuks commonly lay down during rain; this probably serves to reduce heat loss. Most individual daily activity patterns showed some degree of alternation between feeding and ruminating, which is probably characteristic of ruminants generally. In the pooled data, this is evident qualitatively in gerenuks, particularly males, but it is difficult to substantiate quantitatively. In both species, females spent more time feeding than males in the daytime.