BACKGROUND While research has demonstrated that aged persons may show impaired thermoregulatory control, we do not know whether dysthermia in the aged results from altered behavioral or autonomic responses. Consequently, we investigated age-related differences concerning the ability to regulate room temperature. METHODS Two groups of matched healthy males (22.9 yr and 66.9 yr) were subjects of this study. After equilibration at 24 degrees C (rh 50%), chamber temperature controllers were set into cooling mode. Using a dual position switch, subjects adjusted this temperature when air temperature moved outside their preferred range. Switch operation resulted in maximal cooling or heating, without a steady state. Subjective ratings of thermal sensation, discomfort, and affect were provided at each activation. RESULTS Both groups controlled temperature equivalently: 24.9 degrees C (+/- 1.3, young) and 24.5 degrees C (+/- 1.5, elderly; p > .05). At cold-induced change points, the skin temperatures of the calf, thigh, chest, and hand were significantly lower in the elderly subjects. During the heat-induced changes, chest, hand, upper arm, and mean skin temperatures were also lower (p < .05). At cold-induced change points, the elderly group felt colder (p < .05), were less uncomfortable (p < .05), and felt better than the young subjects (p < .05). During heat-induced changes, thermal sensation was equivalent, the elderly were more comfortable (p < .05), and felt better (p < .05). CONCLUSIONS Assuming thermal discomforture drives behavior, it is possible that elderly people may require a more intense thermal stimulus to elicit the appropriate behavioral responses in the home. It is also possible that such stimuli will result in a greater heat flow, elevating the risk of dysthermia in the aged.