1. Cooling constants and thermal conductances are calculated from the rates of cooling of three Conolophus subcristatus, the Galapagos land iguana. 2. The observed conductances are lower than those of comparably large lizards including the Galapagos marine iguana, Amblyrhynchus cristatus. Possible reasons for this difference are considered, especially the effect of air speed on cooling rates. 3. The advantage of low conductance for extended foraging and/or digestion in ectotherms employing temperature-dependent metabolic processes is discussed.