The Avalon Peninsula caribou (Rangifer tarandus) herd in Newfoundland increased from 720 animals in 1967 to 3,000 animals in 1979, a mean rate of increase of r=0.12. The mean adult sex ratio was 39 males: 61 females and 73% of females were parous. Calf recruitment averaged 25% and adult mortality was estimated at 14%. The herd expanded at a relatively constant growth rate with no evidence of a logistic growth curve as density increased to 2.0 caribou/km2. The rapid increase of the herd and the attainment of such a high density is consistent with the view that predation is an important natural control limiting the growth of many caribou herds in North America.