Rates of evaporative water loss and oxygen consumption were measured for the 0.37 g gekkonid lizard, Sphaerodactylus beattyi, and the results compared with those reported previously for a 0.45 g form, S. macrolepis, (Snyder, 1975). Water loss for S. beattyi was 37% lower than for S. macrolepis and the difference was accounted for by a lower rate of cutaneous water loss. Rates of respiratory water loss and oxygen consumption were comparable for the two species. The two species are parapatric on the island of St. Croix and the differences in rates of water loss are reflected in their ecologic distribution on the island.