Direct measurements of distances to nearest neighbor indicated that small, larval Ambystoma gracile were disproportionately associated with small nearest neighbors. Median dis- tance between small animals was significantly less than that between large, neotenic animals and small nearest neighbors; median distances between either size class and large nearest neighbors were even greater. Small salamanders were relatively less likely to be found in deeper parts of the inhabited area. The results indicate size dependent spacing behavior. With recent interest in the synthesis of behavior, ecology, and evolutionary the- ory (Wilson, 1975), interactions between individuals have become important ob- jects of study. Studies of amphibians have revealed such phenomena as territoriality (Emlen, 1968, 1976), feeding hierarchies (Boice and Witter, 1969; Licht, 1973), sib- ling recognition (Waldman and Adler, 1979; Blaustein and O'Hara, 1981) and dear enemy interactions (Jaeger, 1981). Many of these individual interactions are manifest in spatial patterns as individuals attack, avoid, attract, or ignore each other. There have been few field studies on within population spatial distribution of caudate amphibians, however, and to my knowledge none on aquatic salamanders. The purpose of this report is to describe the relationship between larval and neo- tenic Ambystoma gracile as exhibited by the