The dynamics of the giraffe population of the Serengeti were quantified to ascertain the response of the population to the increasing biomass of the available browse resource. Aerial counts conducted in 1971 and 1976 together with analyses of fecundity and mortality data suggest a rate of population increase of some 5–6% per annum. Compared with the dynamics of a stable giraffe population in Nairobi National Park, the sub-adult components of the Serengeti regional populations are larger and juvenile growth rates marginally faster: calving intervals are shorter and the age of first conception younger, resulting in higher fecundities per adult female: calf survival rates are higher and adult mortalities lower. These criteria suggest that the Serengeti giraffe population is expanding as a consequence of its increasing food availability, implying that the population may previously have been food-limited.