Six isolates of Laccarialaccata, S-167 from a forest nursery and S-238, S-283, S-326, S-444, and S-472 from natural forests, were analyzed for acid phosphatase, alkaline phosphatase, and nitrate reductase activity, acid phosphatase isozyme patterns, and IAA and cytokinin production. Differences in enzyme activity and phytohormone production were prominent among the isolates. The patterns of acid phosphatase isozyme could be clearly divided into three host-related groups. Two polymorphic gene loci could be identified as coding for enzymes of acid phosphatase. Two of these gene loci, Acp-b and Acp-c, are characterized by mostly constant, host-dependent frequencies. The other, Acp-d, exhibits allele frequencies related to different habitats. Five isolates share the same Acp-a habitat. Four isolates share the Acp-b habitat, two the Acp-c habitat, and only one isolate, S-238, was from a high elevation at the Acp-d habitat. The isolate from a forest nursery differed strikingly in several characteristics from the other isolates, all of which were from a natural forest. This suggests that nursery soilmanagement practices may select for particular edaphic ecotypes of mycorrhizal fungi.