Certain previous studies suggest, and it is hypothesized herein, that heat balance (i.e., when heat loss is matched by heat production) is attained before the stabilization of body temperatures during cold exposure. This phenomenon is explained through a theoretical analysis of heat distribution in the body applied to an experiment involving cold water immersion. Six healthy and fit males (mean ± SD of age = 37.5 ± 6.5 yr, height = 1.79 ± 0.07 m, mass = 81.8 ± 9.5 kg, body fat = 17.3 ± 4.2%, VO_2max = 46.9 ± 5.5 L^.min^-1) were immersed in water ranging from 16.4 to 24.1°C, depending on body fatness, for periods ranging from 4 to 10 h. Skin temperature reached a near steady state after 15 min of immersion. Core temperature underwent an insignificant transient rise during the first hour of immersion, then declined steadily for several hours, although no subject reached a value of 35°C. Despite the continued decrease in core temperature, shivering reached a steady state of ~ 2 x resting metabolism after the first hour of immersion. Heat debt peaked at 932 ± 334 kJ after 2 h of immersion indicating the attainment of heat balance and confirmation of the hypothesis, but unexpectedly proceeded to decline at about 48 kJ^.h^-1 indicating a recovery of mean body temperature. These observations were rationalized by introducing a third compartment of the body, comprising fat, connective tissue, muscle, and bone, between the core (viscera and vessels) and skin. Temperature change in this 'mid region' can account for the incongruity between the body's heat debt and the changes in only the core and skin temperatures. The mid region temperature decreased by 3.7 ± 1.1°C at maximal heat debt and increased slowly thereafter. The reversal in heat debt might help explain why shivering drive failed to respond to a continued decrease in core temperature, as shivering drive might be modulated by changes in body heat content.