Changes are reported in the population dynamics and physical condition of mountain goats (Oreamnos americanus) following a reduction in their density at Olympic National Park, Washington, U.S.A. The goat population showed density-dependent responses in initial breeding ages and in litter size. Production and recruitment of kids were more variable at high densities, and these population attributes may show nonlinear density dependence. These shifts in dynamics were associated with increases in live weights and, possibly, in fat reserves. The density dependence shown was insufficient to compensate for removals that approximated the initial production of young, and goat numbers declined precipitously. The implications of these relationships to mountain goat ecology are examined.