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The accuracy of using cementum layers in teeth to reconstruct reproductive histories has been evaluated for black bears (Ursus americanus) but not for brown bears (Ursus arctos). We tested the hypothesis that years when brown bears successfully reared cubs could be identified in teeth by a cementum layer that was thinner than layers in either the preceding or the following year. Using teeth from 29 brown bears with known reproductive histories, we identified potential cub-rearing years ('cub years') based on measurements of cementum layer thickness and compared results to known years of cub rearing. Of 62 known years when females reared cubs, only 13 were correctly identified. We failed to identify 49 known cub years, and we incorrectly identified as cub years 30 years when females did not rear cubs. We concluded that this method, though successful for black bears, was unreliable for brown bear populations.