Effects of water temperature and flavoring on fluid consumption and body weight losses were studied in fourteen unacclimatized men (21-33 years) during 6 hr of treadmill exercise (4.8 km.hr-1, 5% grade for 30 min.hr-1) in a hot environment. Subjects consumed each of four beverages (15 degrees C water, 40 degrees C water, 15 degrees C flavored water, and 40 degrees C flavored water) on four nonconsecutive days. We identified two groups of individuals by body weight (BW) loss during the cool water trial: drinkers (D) who lost less than 2% initial BW (0.80 +/- 0.15%) and reluctant drinkers (RD) who lost more than 2% (2.53 +/- 0.12%). Although sweat losses were not different between the two groups, D consumed 31% more cool water than RD and experienced 68% less BW loss. Compared to the warm water trial, 6 hr consumption of cool water was significantly increased in both D (59%) and RD (141%) and BW loss was dramatically reduced in both groups. Flavoring significantly enhanced warm water consumption and reduced BW loss in RD only. Reduced consumption of warm water increased rectal temperature, heart rate and plasma osmolality in both groups. The results of this study indicate that either flavoring or cooling warm water will enhance fluid intake and reduce body weight deficits in men reluctant to drink.