The current knowledge of sexual reproduction of Cryptococcus gattii from a population genetics perspective is reviewed in this chapter. In genetic studies, cryptic species are usually detected as exclusive groups of organisms occupying strongly supported branches on phylogenetic trees that have been derived from different, independent loci. Assessing the relative numbers of α and a cells is therefore an important aspect of determining if populations are likely to have undergone sexual recombination. The initial studies of mating type in C. gattii found 84% of clinical isolates to be of the α mating type. Mating type was assessed by coculture with tester strains, and the majority of strains (~90%) were fertile, producing basidia and basidiospores. Amplified fragment length polymorphisms (AFLPs), which are highly discriminatory molecular markers, were therefore selected to establish multilocus genotypes. The population genetics of clinical collections is generally more complicated than the study of environmental populations as humans travel and may acquire an infection far from where they eventually present with clinical disease and an isolate is obtained. The pattern of pairwise compatibility among global VGII isolates presents a striking contrast to that seen in VGI. All VGII populations studied to date are heavily biased for one or the other mating type, and the most probable scenario is that mating occurs between isolates of the same sex.