The incidence of heat illness and heat stroke is greater in older than younger people. In this context, exercise training regimens to increase heat tolerance in older people may provide protection against heat illness. Acute increases in plasma volume (PV) improve thermoregulation during exercise in young subjects, but there is some evidence that changes in PV in response to acute exercise are blunted in older humans. We recently demonstrated that protein-carbohydrate (Pro-CHO) supplementation immediately after a bout of exercise increased PV and plasma albumin content (Alb(cont)) after 23 h in both young and older subjects. We also examined whether Pro-CHO supplementation during aerobic training enhanced thermoregulation by increasing PV and Alb(cont) in older subjects. Older men aged 68 years exercised at moderate intensity, 60 min day(1), 3 days week(1), for 8 weeks, at 19 degrees C, and took either placebo (CNT; 0.5 kcal, 0 g protein kg(1)) or Pro-CHO supplement (Pro-CHO; 3.2 kcal, 0.18 g protein kg(1)) immediately after exercise. After training, we found during exercise at 30 degrees C that increases in oesophageal temperature (T(es)) were attenuated more in Pro-CHO than CNT and associated with enhanced cutaneous vasodilatation and sweating. We also confirmed similar results in young subjects after 5 days of training. These results demonstrate that post-exercise protein and CHO consumption enhance thermoregulatory adaptations especially in older subjects and provide insight into potential strategies to improve cardiovascular and thermoregulatory adaptations to exercise in both older and younger subjects.