Wheat plants were grown under constant conditions of light intensity, daylength, and humidity at controlled day temperatures of 5, 10, and 20 °C. Selected plants were harvested at three stages of growth for analysis of the levels of four enzymes (aspartate and alanine aminotransferases, glutamic dehydrogenase and glutamic decarboxylase) and of free amino acids. The effect of growth temperature on enzyme levels was most marked in the case of glutamic decarboxylase, which showed highest activity in plants grown at 5°C. The concentrations of most free amino acids also were highest in plants grown at 5 °C, irrespective of the stage of plant development.