Abstract: The role of Pseudomonas fluorescens strain D93, a genetically engineered microorganism, was compared with its metabolites. This biocontrol agent protected roots of wheat from attack by the take-all pathogen and stimulated growth of wheat in the greenhouse experiments conducted in Beijing. Seed treatment with the bacteria and the sterile metabolites reduced the disease severity by 4.8% and 27.8%, respectively. Soil treatment with the metabolites and the bacteria increased the fresh top weight of wheat seedlings by 34.5% and 7.5%, respectively. The results indicate that if used at the same concentration, the bacteria are better than the metabolites in disease suppression, while the metabolites are more suitable than the bacteria for plant growth stimulation. The effect of metabolites was influenced by the ingredients of the culture media. The disease-inhabiting ability of the metabolites produced in potato dextrose was greater than that of the metabolites produced in nutrient broth yeast. In contrast, the ability of the former to stimulate wheat growth was weaker than that of the latter. It was concluded that some unknown materials in the metabolites of strain D93 were involved in disease suppression and wheat growth stimulation.