Allele and genotype frequencies for the highly polymorphic D1S80 locus were determined in a Finnish population sample by using PCR followed by high-resolution PAGE and silver staining, a procedure called the amplified-fragment-length polymorphism (Amp-FLP) technique. In 140 unrelated Finnish individuals 15 alleles and 43 phenotypes were observed. The D1S80 locus demonstrated a heterozygosity of .77, and the power of discrimination was .92 in this sample representing a genetically isolated Finnish population. The distribution of observed genotypes conformed to Hardy-Weinberg expectations. In 36 mother-child pairs Mendelian inheritance for the alleles at the D1S80 locus could be demonstrated in all cases, and no mutations were observed. The usefulness of the D1S80 locus for forensic casework was assessed by using Amp-FLP analysis of the D1S80 locus in 36 forensic cases including 18 rapes, 14 homicides, and 4 other violent crimes. In most cases valuable information was obtained using the Amp-FLP technique, and in no case was there indication of either false-positive or false-negative results.