Validation studies were carried out on the short tandem repeat (STR) locus D12S391 including the determination of the allele frequencies, forensic application and sequence analysis of variant alleles. A total of 16 alleles were found in a population survey of 158 unrelated individuals from the Rhine area, none of which exceeded the 0.20 frequency level. In 316 alleles analysed so far 18 alleles were found with an incomplete repeat unit in the 5'-end of the repeat region. The statistical values were similar to those of other European populations and no deviation from Hardy-Weinberg equilibrium (HWE) was observed.