This study examined whether regional differences in the lipid composition of bowhead whale blubber support the hypothesis that blubber plays a role in the energetic strategy of regional heterothermy in the bowhead whale. The sub gross and microscopic structure and chemical composition of blubber cores, from representative areas of 4 bowhead whales (2 male and 2 female) were determined. Efforts were also made to establish whether a relationship exists between blubber structure, chemical composition, and depth from skin surface and/or location on the body of the whale. The blubber of the bowhead whale shares many morphological and chemical features with the fin and sei whale. There are, however, distinct differences. One of these, the highly saturated lipid composition of the blubber of the lower lip of the bowhead whale, may be important in evaluating regional heterothermy strategies of the bowhead whale. These studies also suggest that blubber lipid composition with regard to chain length, degree of unsaturation and thermal transition state is not uniform at all depths of the blubber in the bowhead whale. This study was supported by a grant from North Slope Borough, Department of Wildlife Management, Barrow, Alaska.