The metabolic thermogenic curves of mitochondria isolated from fish liver tissue have been determined by an LKB 2277 Bioactivity Monitor. The metabolism activity of mitochondria inhibited by sodium azide has also been studied. The thermogenic curves can be divided into four parts: the lag phase, active recovery phase, stationary phase, and decline phase. From these thermogenic curves, the recovery rate constant k(1), decline rate constant k(2), the maximum heat production rate P-m, heat output Q are obtained. The metabolic heat released, time of each phase, rate constants, and shape of the thermogenic can be significantly influenced by sodium azide added. These results suggest that sodium azide inhibits the metabolism of mitochondria, and the inhibition is incomplete. The inhibitory effect reaches the maximal value with the exactly sodium azide concentration of 2 mu g mol(-1).