There are several different types of self-incompatibility in different flowering plant species, and there has recently been progress in understanding their molecular genetics by using combined molecular and evolutionary approaches. Questions include the mechanism of self-incompatibility (both the nature of the proteins encoded by the genes and whether incompatibility systems all have separate genes for the pollen and pistil recognition proteins, which is the focus of this mini-review) and whether these systems involve chromosome regions with suppressed recombination and, if so, the size of these regions.