Short tandem repeat studies are powerful tools for parentage analysis and for identification of missing persons, victims of murder, and victims of mass fatalities when reference samples are unavailable. The primer in the Identifiler kit failed to amplify an allele at the D19S433 locus, producing a silent ("null") allele. The causal mutation is a base change (G>A) 32 nucleotides downstream from the 3' end of the AAGG repeats. The silent alleles are problematical in parentage analysis because when transmitted, they can cause a parent-child inconsistency that is unrelated to Mendelian genetics. The inconsistency is sometimes termed an "apparent opposite homozygosity" and it produces false evidence of nonparentage. Alternative primers were designed to amplify the D19S433 locus alleles and they detect the silent allele. Frequencies of the (no longer) silent allele were determined to be 0.0114 in 176 people from Shizuoka (Honshu) and 0.0128 in 156 people from Okinawa.