Allele and phenotype frequencies for two tetranucleotide STR (short tandem repeat or microsatellite) systems, HUMvWFA31/A and HUMF13A01, were obtained from a sample of approximately 240 unrelated individuals randomly selected from the French Caucasian population. PCR (polymerase chain reaction) products were analysed on 6% polyacrylamide denaturing gels and visualized using fluorescently labelled primers on the automated 373A ABI DNA sequencer (Applied Biosystems Inc.). French Caucasian allele frequencies were compared to other published Caucasian data. Conditions were optimised for the quadruplex PCR amplification of these two STR loci together with the HUMFESFPS and HUMTH01 loci and the quadruplex PCR was also performed on various forensic DNA samples.