Flow-sorted chromosome 18 material from the pig (SSC18) was amplified with SINE-PCR to generate DNA for molecular cloning. An SSC18-enriched library was constructed and subsequently screened with a (CA)15 probe to identify polymorphic microsatellites. Eleven unique micro-satellites were obtained, six of which constituted direct extensions of SINE poly(A) tracts. Eight primer pairs amplified polymorphic loci in unrelated pigs. The polymorphic markers were typed in a Swedish reference pedigree for porcine genome mapping, but only two of them (SO177 and SO179) mapped to SSC18. The remaining markers mapped to chromosomes 3, 4, 7, 9, and 11. Together with two markers from other sources (S0062 and sw787), a four-point linkage group on SSC18 could be established.