One of the more widely studied simple repeat sequences in the mammalian genome is the (dG-dT)n.(dC-dA)n dinucleotide repeat sequence. As these repeats are highly polymorphic and fairly evenly distributed in diverse mammalian genomes, they constitute a very powerful tool for genetic mapping in a wide variety of species. So far, the knowledge about repeat sequences in the porcine genome is sparse and only a few areas of this genome have been sequenced. We have isolated and characterized 108 porcine (dG-dT)n.(dC-dA)n sequences and studied the distribution of these, both by investigating random clones and by performing in situ hybridization. A remarkable correlation between humans and pigs was found with respect to the structure, to the number of repeat blocks, and to the chromosomal distribution.