Despite the potential constraints imposed by cutaneous respiration and nocturnality, some salamanders actively thermoregulate when conditions permit. We measured substrate temperature selection in two species of Desmognathus in a moist thermal gradient in the laboratory. Desmognathus monticola selected significantly higher temperatures than Desmognathus quadramaculatus. Although the substrate temperatures selected by D. quadramaculatus did not vary over time (mean ± 1 SE = 13.6 ± 1.1 C), D. monticola selected significantly higher temperatures at night than during the day. Mean temperatures selected by D. monticola were 14.0 ± 1.5 C from 1200–1600 h and 19.7 ± 1.6 C from 2000–0000 h. This difference in temporal patterns is consistent with field behavior, because D. monticola is more frequently found away from water at night than is D. quadramaculatus.