Allele and genotype frequencies for the 3'-ApoB locus were determined in a population sample from Catalonia (northeast Spain) using PCR amplification and nonradioactive detection. In a total of 308 unrelated individuals, 16 alleles and 50 genotypes were observed. The 3'-ApoB locus demonstrated a heterozygosity of 80%. The distribution of genotypes is in agreement with expected values according to the Hardy-Weinberg equilibrium.