Following acclimation at 20° or 6° and exposure at -6° levels of enzyme activities were studied in larvae of Ephestia kuehniella. The activities of glucose-6-phosphate dehydrogenase, catalases, proteinases and acetylcholine esterase were all affected by the acclimation temperatures. Some enzymes, like 6-phosphogluconate dehydrogenase and acid phosphatases, showed different levels of activity after exposure at -6° depending on previous acclimation. After exposure at -6° the activities of 6-phosphogluconate dehydrogenase, acid phosphatases and acetylcholine esterase in larvae injected with glycerol were similar to those of larvae acclimated at 6°. Oxygen consumption and activities of isocitrate dehydrogenase and trehalase were not influenced by previous temperature treatments. It appears that various enzymes are affected in different ways by acclimation and exposure at low temperatures. It is suggested that a better balance of various enzyme activities are maintained at low temperatures in larvae acclimated at 6° or injected with glycerol. The results also indicate that resistance acclimation in this species is regulated by mechanisms that do not include capacity acclimation.