Healthy adult male Beagles (n=24) were used to assess metabolizable energy (ME)required for maintenance as a function of ambient temperature. First, ME requirements were determined in summer (mean temperature,28°C), fall (18°C) and winter (8°C) using four dogs from a litter (16 mo of age,11-12 kg in body weight) and the other four from another litter (50 mo of age,14-15 kg) in every season. The ME density of experimental diets was determined by a digestion trial using additional four adult male Beagles (15kg). The diets were fed for 4 wk in a season, and daily intakes were adjusted to four levels to give dififerent weight gains ranging from negative to positive within a group. Maintenance requirements of ME were regarded as the ME intake that makes gains zero. As a result, maintenance requirements of ME (kcal/W^0.75perday) were as follows in the order of 16 and 50 mo of age: 100 and 87 in summer,135 and 108in fall, and 161 and 146 in winter. Young dogs required more ME for maintenance than older dogs in all seasons. Next, linear regressions were detemined between the ME requirement for maintenance and the mean temperature in three seasons. The regressions were significant(P<0.01)for each age group and even when data were pooled independent of age, and suggested that daily ME required for maintenance could increase by 3.0kcal/W^0.75 every1⋅°C drop in temperature within the range of 8 to 28°C.