We present a new, plaster model for measuring operative environmental temperature (T_e) and water loss of amphibians with little or no cutaneous resistance to water loss. These models are made from molds of live animals, cast in plaster of Paris, and can be fitted with water reservoirs that allow them to be used for extended periods. Plaster models did not differ significantly in T_e or water loss rate from either identically shaped models made of 3% agar and measured in a wind tunnel or from live cane toads (Bufo marinus) measured outdoors in a variety of conditions. Thus, plaster models offer an accurate measure of both T_e and water loss across a range of environmental conditions. The plaster models are also relatively simple to make and offer several advantages over other model types, in that they are durable, they do not shrink like agar models, they can be colored to match absorptivity of live animals, and they can be made in postures representative of live animals.