Oxygen consumption in lungless salamanders of the family Plethodontidae was compared with oxygen consumption in lunged salamanders of the families Ambystomatidae and Salamandridae, by a modified manometric method. The relationship of body surface area to weight in these animals was measured by skinning and measuring the skin surface with a polar planimeter. There was no significant difference in the weight-surface area relationship for lunged and lung-less salamanders. The weight-surface area relationship in salamanders is expressed by: S = 8.42 W0.694, where S is surface area in cm2 and W is weight in grams. Lunged salamanders had a higher metabolism than lungless forms at temperatures above 10[degree]C. Comparison of the weight-metabolism relationship showed that the slope for lunged animals (0.856) was significantly greater than that for lungless forms (0.72). Weight-respiratory surface area relationships showed that the slope for lunged forms (0.794) was greater than that for lungless species (0.614). The marked correlation between respiratory surface area and metabolism in salamanders indicates that the probable ultimate limit to metabolism in salamanders is the total respiratory surface area available for gas exchange with the environment.