Three concepts are introduced and defined. They are (1) absorption threshold, which is the level of the substrate moisture above which there is a net gain in body weight of dehydrated salamanders and below which there is a net loss, (2) critical level, which is the substrate moisture below which water loss from amphibians increases markedly, and (3) limiting range, which includes all substrate moisture values between the above 2 points. The absorption threshold for Plethodon cinereus is between 1 and 1.5 atm moisture tension or a pF of slightly over 3. The critical level for the same species is at approximately 2.5 atm (pF of 3.4) and coincides with the point at which there is a sharp increase in soil moisture tension and decrease in relative humidity of the soil interstices. Above the absoprtion threshold rates of water uptake by P. cinereus is correlated with soil moisture if comparison is made between soil samples with a sufficiently different moisture content that they do not have similar tensions. Absorption is faster at 23 C than at 16 C. Rate of absorption if weakly correlated with size of animal. As compared with the roots of vascular plants, salamander skin has weak absorptive powers and both the absorption threshold and critical level for P. cinereus are lower that the wilting coefficient for plants. This is compensated for by its behavioral responses to desiccation which tend to keep it in favorably moist situations or to conserve water.