The efficacy of strains of <i>Glomus claroideum</i>, <i>G. etunicatum</i>, and <i>G. mosseae</i> was evaluated on the growth of BSR201, Iowa2052, and Peking soybeans (<i>Glycine max</i>, L.). The fungal strains were isolated from two soybean fields that have Clarion (a well drained fine-loamy, mixed, mesic Typic Hapludoll) and Webster (a poorly drained fine-loamy, mixed, mesic Typic Endoaquoll) soils. The strains used included five strains of <i>G. claroideum</i>, two strains of <i>G. etunicatum</i>, and one strain of <i>G. mosseae</i>. The inoculated 10-wk-old plants produced significantly higher shoot dry weights and seed numbers per pot than noninoculated plants. The increase in growth depended on both the host cultivar and the infecting AM fungal strain. Isolates of <i>G. claroideum</i> and <i>G. etunicatum</i> originally from Clarion soils typically increased shoot dry weight more than did the isolates of either <i>G. etunicatum</i> or <i>G. mosseae</i> derived from Webster soil. Plants produced higher shoot dry weights when they were grown in the presence of <i>G. mosseae</i> than they did when inoculated with isolates of either <i>G. claroideum</i> or <i>G. etunicatum</i> when the isolates were derived from Webster soil. Isolates of <i>G. claroideum</i> and <i>G. etunicatum</i> from Clarion soils generated higher dry weight in Peking plants (77 to 90% increase above the controls) than did the isolates from Webster soils (31 to 65% increase). BSR201 plants, on the other hand, reached their highest shoot dry weight when they were inoculated with <i>G. claroideum</i> strains obtained from Webster soil (77 to 103% increase). Mycorrhizal colonization of the inoculated roots was confirmed. Large spore populations greater than 50 spores g^-1 soil were found in the pots after harvest. Pots with one <i>G. etunicatum</i> strain contained about 20% of contaminating <i>G. vesiforme</i>-like spores, but spores of the remaining strains were verified as being of the same species as the introduced spores.