This thesis examines the effects of the plant growth-promoting fungus, 'Trichoderma harzianum' T-22 (T-22) and arbuscular mycorrhizal fungi (AMF) on the growth of transplanted tallgrass prairie plant species. Inoculation with AMF had a variable effect on tallgrass prairie plant species, ranging from a 35% decrease to a 36% increase in growth. T-22 did not have a growth-promoting effect on any of the species tested in the greenhouse or field. Also, T-22 did not cause a significant reduction in AMF colonization in this study, despite the fact that T-22 is considered to be a mycoparasite and can aggressively attack other fungi, including AMF. The results of this thesis indicate that T-22 did not appear to have biologically significant adverse or beneficial effects on the tallgrass prairie plants tested and may not be an effective agent to promote the growth and success of prairie restoration projects.