Abstract: Stem and root-rot caused by Bipolaris spp., lead to significant yield losses of wheat (Triticum aestivum L.) in Hamadan province, Iran. One strategy to control stem and root-rot is the use of antagonistic, root-colonizing rhizobacteria. In order to assess the potential of rhizospheric microorganisms in biological control of such soil-borne diseases, in this study one hundred eighty isolates of both Pseudomonas and Bacillus spp. from rhizoplane and surrounding soil of healthy and infected wheat, were collected. Among them, by using the dual culture method, only 9 isolates with the most antagonistic ability against the growth of two pathogenic fungal species (Bipolaris australiensis and B. sacchari (were selected and purified. According to the results of biochemical and physiological tests, they were identified as three biovar of Pseudomonas fluorescens and some species of Bacillus; B. subtilis, B. coagulans, B. licheniformis, B. megaterium and B. brevis. Production of antifungal substances and volatiles metabolites, siderophores and secretion of lytic enzymes such as protease and cellulase as the inhibitory mechanisms in vitro were evaluated. Furthermore, in greenhouse conditions the effects of antagonistic rhizobacteria on disease severity and incidence caused by Bipolaris australiensis and B. sacchari, using seed coating and soil drenching were studied. Statistical analysis of data indicated that, treating wheat seeds with some of the antagonistic rhizobacteria, not only reduced the disease severity and incidence, comparing with the control, but also had showed positive influence on growth and yield of wheat cultivars.