The genotypes of 107 strains of Cryptococcus isolated from the environment or from patients from various geographical areas were determined by multilocus enzyme electrophoresis (MLEE). We analyzed the relationships between genotype structure and serotype and between genotype structure and strain origin. Twelve of the 14 enzyme-encoding loci studied were polymorphic, giving rise to 48 electrophoretic types. The genotypes of C. neoformans and C. laurentii were very similar. MLEE could not distinguish between these two pathogenic species. A correlation between the genetic multilocus structure and the origin of the sample (from the environment or patients) existed. A second analysis detected a correlation between genotype distribution and serotype. The second analysis considered three serotype groups (B, C, and A plus D plus A/D), proving that serotypes A, D, and A/D are closely related. MLEE is a useful epidemiological tool for improving our understanding of the biology of this fungus