DNA from the short tandem repeat (STR) system HUMTH01 was amplified by the polymerase chain reaction (PCR) and analyzed by vertical electrophoresis in polyacrylamide gels followed by silver staining. DNA samples from 100 unrelated Danes, 147 unrelated Greenland Eskimos, and 89 Danish mother/child pairs were analyzed. Significant differences were observed between the distribution of fragments ('alleles'), whereby allele number 7 was considerably more frequent in Eskimos (0.687) than in Danes (0.201). The distributions of HUMTH01 phenotypes were in Hardy-Weinberg equilibrium in both the Eskimo and Danish populations. In the 89 Danish mother/child pairs, the segregation of the HUMTH01 genotypes was in accordance with the genetic model of co-dominant inheritance and no mutations were found. In a blind trial, DNA samples from 40 unrelated Danes were investigated by one of us in Copenhagen, at the FBI Forensic Science Research and Training Center (FSRTC), Quantico, and at the Institut für Rechtsmedizin, Münster, Germany. Concordant HUMTH01 types were found in 39 out of 40 individuals. The allele which led to discrepant typing results was assigned type 9.3 in two laboratories and type 10 in one laboratory.