Studies of interspecific competition for space among stream-dwelling salmonid species have employed a variety of methods, most of which have centered on identifying species differences in microhabitat use. Clear demonstration of competition, however, generally requires evidence that interactions produce a niche shift in one or both species. Laboratory channels or aquaria have frequently been used in controlled experiments concerned with salmonid competition. Field measurements typically involve scuba diving or snorkeling techniques, although carefully managed electrofishing studies have also demonstrated habitat differences between species. Stream dwelling salmonid populations may be limited at different times by competition, predation, or climatic events such as droughts or floods. When populations are limited by processes other than competition, competition is of minimal intensity or nonexistent. Long-term coexistence of sympatric species may be partly facilitated by species differences in habi...