The fragment length polymorphism YNZ22 (D17S5) was analysed for a sample of 207 unrelated individuals living in Madrid (Spanish Caucasians) using PCR-methodology and high resolution separation. Hardy-Weinberg expectations (HWE) were calculated after pooling alleles into four groups. No deviations from HWE were detectable using the conventional chi 2-test. The power of discrimination was estimated as 0.96 and the mean paternity exclusion chance as 0.7587. A comparison of the allele frequency distribution with those of other Caucasian groups revealed no major differences.