Abstract Self-incompatibility in Brassica species is controlled by a single S locus with multiple alleles. Recent experimental data suggest that SLG ( S locus glycoprotein) and/or SRK ( S receptor kinase) are the stigmatic S determinants of self-incompatibility in Brassica . A 76-kb genomic fragment containing both SLG and SRK was isolated and characterized in the S 9 haplotype of B. campestris . This fragment contains at least 14 expressed genes and three putative open reading frames (ORFs), suggesting that the S locus is embedded in a gene-rich region. Within this fragment, both anther and/or stigma-specific genes are clustered around the SLG and SRK genes. Some members of the S multigene family are also closely linked to the S locus. In this review we discuss the complex genomic structure of the S locus in Brassica species.