Resting metabolic rate of pygmy rabbits (0.89 ml 02 g-1 h-1) was high compared to other eutherian mammals, but not unusual among lagomorphs. The estimated size of the zone of thermoneutrality was ca. 8-90C, with the lower critical temperature occurring between 15 and 200C, depending on body mass. Minimum thermal conductance was lower and mean body temperature was higher than predicted for similarly sized mammals. Body temperature fluctuated > 1?C within a 24-h period, but showed no circadian patterns. Pygmy rabbits are thermally stressed during harsh winters in Wyoming, but low thermal conductance, a highenergy source of food, and favorable microenvironments enhance survival. Published in Journal of Mammalogy, volume 78, issue 4, on [...]