Characteristics and structures of mt SSU rDNA were investigated for the phylogenetic study of Ganoderma. Phylogenetic information was concentrated mostly in the V1, V4, V5, V6 and V9 variable domains, but informative sites in conserved domains also significantly contributed in resolving phylogenetic relationships between Ganoderma groups. Secondary structure information of variable domains was found to be a useful marker in delineation of phylogenetic groups. Strains of Ganoderma species used in this study were divided into six monophyletic groups. Ganoderma colossus made a distinct basal lineage from other Ganoderma species and Tomophagus, created for G. colosuss, appeared to be a valid genus. Ganoderma applanatum and G. lobatum classified in subgenus Elfvingia made a monophyletic group. Ganoderma tsugae from North America and G. valesiacum from Europe, both living on conifers, were closely related. Ganoderma oregonense and strains labeled G. lucidum from Europe and Canada were grouped with G. tsugae and G. valesiacum. Strains labeled G. lucidum living on hardwoods from the United States and Taiwan were grouped with G. resinaceum, G. pfeifferi and G. subamboinense var. laevisporum, and they all produced chlamydospores. Two strains labeled G. lucidum and three strains labeled G. resinaceum from America were concluded to be conspecific. Strains labeled G. lucidum from Korea and Japan were monophyletic and were distinguished from strains labeled G. lucidum from Europe and North America. Host relationships and the presence of chlamydospores in culture proved to be important characteristics in the systematics as well as the phylogenetic relationships of Ganoderma.