Female pseudohermaphroditism is characterized by gonads consistent with chromosomal sex combined with ambiguous, masculinized external genitalia. Recognized in many mammals, this condition results from fetal exposure to androgens that can be embryonic, maternal, or environmental in origin. Female pseudohermaphrodite black and brown bears (Ursus americanus and U. arctos) from Alberta, Canada, and polar bears (U. maritimus) from Svalbard, Norway, have been identified. Recent population surveys in Nunavut, Canada, led to the discovery of 11 additional female pseudohermaphrodite polar bears. Each bear was screened for the presence of sex-determining region-Y (Sry) and amelogenin-Y (AMELY) genes as indicators of Y-chromosome DNA. One bear possessed both genes, implying that trisomy or a chromosomal rearrangement may account for her virilized phenotype. Preliminary data suggested that Sry was also present in the other 10 bears; further testing disproved that result, revealed an important source of error when using polymerase chain reaction (PCR) to screen for the Sry gene, and led to the development of new amelogenin primers that provide superior sex information for bears. Ultimately, these extensive screens also supported the conclusion that 10 of 11 morphologically abnormal individuals may possess no genuine male-specific DNA. Therefore, nongenetic mechanisms such as maternal tumors, freemartinism, or endocrinological effects of environmental contaminants may also influence the development of the female pseudohermaphrodite phenotype in Nunavut polar bears.