The concept of carrying capacity has gained broad currency, although some population ecologists are dubious about its value. This paper assesses the utility of the concept and develops an alternative understanding of population growth. First, carrying capacity is viewed in historical perspective and evidence that is supposed to support it is criticized. Then the underlying assumptions upon which it rests are reexamined. Limits to growth are seen to be both multiple and variable. The mechanism that is supposed to regulate population is critically reviewed. And the assumptions of balance in nature and equilibrium in biotic communities are reevaluated. These assumptions having been found wanting, population growth is reassessed in relation to environmental variability. The strategies by which different species cope with variability are described, and the windfall effect, which causes some populations to grow rapidly and then collapse, is identified. Finally, it is suggested that carrying capacity may be a self-validating belief and that is has limited relevance to human population growth, which is better understood in other ways.