Temperature plays an important role in various aspects of the life history and physiology of ectotherms. We examined the effect of temperature on standard metabolic rate in the mud turtle, Kinosternon subrubrum. We measured O 2 consumption and CO 2 production at 20 o C and 30 o C using a flow through respirometery system. Standard metabolic rate was significantly higher at 30 o C (9.25ml O 2 /h, 6.35ml CO 2 /h) compared to 20 o C (2.10ml O 2 /h, 1.96ml CO 2 /h). The Q 1 0 value for O 2 was 5.10, and for CO 2 was 3.40. Our findings generally agree with those of other studies of metabolism in vertebrate ectotherms.