Nuclear ribosomal DNA ITS sequences have been used to investigate phylogenetic relationships between 34 Ganoderma isolates cultivated in China. Five distinct groups were identified: the subgenus Elfvingia, the sect. Phaeonema, and three groups within the sect. Ganoderma. Most of the Ganoderma isolates (85.7%) formed a single group within the sect. Gantoderma. The result indicated clear genetic diversity between the subgenus Elfvingia and the sects Phaeonema and Ganoderma, but a smaller degree of genetic diversity between the three groups placed within the sect. Ganoderma. Analysis of molecular data is a more effective and useful approach for studying the taxonomy of Ganoderma, and for establishing phylogenetic relationships within the genus, compared to methods based on fruiting body morphology.