Allele and genotype frequencies for two tetrameric and two pentameric short tandem repeat (STR) loci (THO1, VWA31/A, CD4, and TP53) were determined in a population sample from northern Portugal. Genotyping of PCR amplification products was done using polyacrylamide gel electrophoresis followed by silver staining; heteroduplex analysis was performed to distinguish THO1 genotypes involving allele 10 and the nonconsensus allele 9.3. For all loci allele frequencies fitted the distribution patterns generally observed in European populations. The observed genotype distributions do not deviate significantly from Hardy-Weinberg expectations, although for VWA31/A a significant excess of heterozygotes involving allele 17 was found. Mother-child pair analyses confirmed the regular Mendelian pattern of inheritance. Because the information content of these systems is high and because their genotyping is technically reliable and simple, CD4, THO1, VWA31/A, and TP53 are appropriate genetic systems for anthropological genetics.