Allele and genotype frequencies for D1S80, 3'ApoB and YNZ22 loci have been determined in a population sample of the North of Portugal using the polymerase chain reaction (PCR) amplification and nonradioactive detection. The distribution of genotypes in the three polymorphisms studied is in agreement with expected values according to the Hardy-Weinberg equilibrium. The combined chance of exclusion for the three systems is 0.96, and the combined power of discrimination is 0.99.