Energy requirement ofCalotes versicolor, as judged by the rate of oxygen consumption by whole body, liver and muscle, was recorded to be minimum during hibernation (quiescent phase) and maximum during breeding phase. Kidney metabolic rate was comparatively high during hibernation and post-hibernation. Statistically significant circannual rhythms were detected in the rate of oxygen consumption of whole body, liver, muscle and kidney but not in that of brain. However, significant but transient increase in the rate of brain oxygen uptake was recorded during February (arousal), May (initiation of breeding) and November (entry into hibernation). It seems that the annual changes in metabolic rate are reflections of energy requirements of the lizard and its tissues during different phases of the annual activity cycle. Further, climatic factors seem to affect the oxidative metabolism ofCalotes acting through the endocrine glands.