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Estimates of the number of polar bear (Ursus maritimus) maternity dens and observations of social interactions were made over 40 days in a dense denning area on Herald Island, Russia, following female emergence from dens. Twenty-six dens were found throughout the accessible areas of the island (density = 6.2 dens/km^2); 11 were concentrated in the Main Valley (12.1 dens/km^2). Females emerged from dens from 17 March (the first observation day) until 31 March 1993. Sixteen females with cubs-of-the-year were observed for 156 hours. Mean litter size was 2.0. Females averaged 15.5 days (range = 8-27) in the denning area from emergence until leaving for the ice. Younger females spent less time outside their dens than older females. Number of dens used other than their own averaged 2.4 dens for all females. Younger females were not observed to use any den other than their own, whereas older females averaged 3.2 dens/female. Females spent considerable time grazing on grasses. Interactions between females defending and competing for dens resulted in spatial separation of family groups and limited access to resources. Presence of other females close to dens sometimes caused a female with cubs to abandon her den. Avoidance of older females by younger females may demonstrate hierarchy in dense denning areas. My observations support the importance of protecting Herald Island and the surrounding marine area as key polar bear breeding and foraging habitats.