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The mark/recapture analyses that are currently used to study polar bears (Ursus maritimus) generally underestimate the average number of cubs per litter and assume that the annual survival of cubs is unity. In this paper, a relationship among the number of yearlings per litter and 2-year-olds per litter is used to derive the survivorship of yearlings, which is then used to solve for the number of cubs per litter. When this relationship was applied to published population data from North America, the resulting estimated survival rates of yearlings ranged from 0.70 to 0.75, and the estimated average number of cubs per litter was between 1.70 and 1.98. These findings indicate that current estimates of sustainable yield for polar bear populations may be in error because the reproductive rate of adult females was likely to be underestimated, and the survival rate of cubs of the year was likely to be overestimated.