Technical Abstract: The use of endophytic organisms to control other endophytic organisms is complicated, but nevertheless viewed as being unique and an important strategy. There are endophytic species of fungi that produce mycotoxins such as Fusarium verticillioides that produces the fumonisins and other toxins, which are potentially harmful to humans, livestock, and poultry. The use of an endophytic biocontrol organism for prevention of mycotoxins during the endophytic state of F. verticillioides depends on the degree of dominance one organism has over the other. The use of the bacterial endophyte Bacillus mojavensis has some promise but predicting success of strains is difficult. A study of niche overlap indices was conducted to obtain a measure of competition between several strains of Bl mojavensis and F. verticillioides, its ecological homologue in maize. The in vitro growth of these two organisms on several carbohydrates as sole carbon sources that are known to exist in maize apoplasm was measured with the Microbiology Reader Bioscreen C and niche overlap indices determined. The results indicated that while F. verticillioides is the more competitive of the two, other factors are responsible for the success of this fungus. Thus, niche overlap indices indicated that nutrient competition is perhaps not as important as the production of other competing factors, e.g., microbial inhibitors, by F. verticillioides for growth within the intercellular spaces of maize.