To determine the sex and identity of individual American minks (Neovison vsion), a species introduced into Japan, molecular genetic methods were employed on fecal samples collected from the Kushiro Wetland, eastern Hokkaido. We examined the sex chromosome-linked genes ZFX and ZFY and 11 microsatellite loci to identify individuals. From microsatellite genotypes, the probability of identity was calculated to distinguish between individuals with 99% certainty. To evaluate the accuracy of the genotyping results, we used two approaches for several randomly selected samples. In the first approach, we genotyped all samples from the results of a maximum of three independent polymerase chain reactions (PCRs). In the second approach, we genotyped 10% of the samples from the results of five independent PCRs. Samples subsequent genotypings disagreed with the first genotype were counted as one of three categories of error. The results indicated that genotyping more than 10 microsatellite loci was required to reduce the probability of error in identity to less than 0.01. Twenty of 72 fecal samples were genotyped at 10 or 11 microsatellite loci and sex-determined by ZFX/ZFY genes, resulting in identification of five males and nine females. In assessing the accuracy of the results, genotyping errors were found to have occurred in 20% of the first genotypes. The main type of error was 'missing data', which can be prevented by increasing the number of replicate PCRs.