Researchers have reported that B. subtilis could secrete several antifungal metabolites such as iturin, surfactin ( Asaka and Shoda 1996) and proteins ( Li et al. 2009). In this work, antifungal activity of B. pumilus N43 was tested against R. solani Q1. In dual culture, the mycelium of R. solani Q1 was inhibited by B. pumilus N43 without direct contact. An antibiotic produced by N43 could contribute to this phenomenon. Micrographs showed that N43 induced hyphal deformation, enlargement of cytoplasmic vacuoles and cytoplasmic leakage in R. solani Q1. Fiddaman and Rossall (1993) observed hyphal vacuolization and deformation in R. solani and in Pythium ultimum after treatment with a B. subtilis strain. A similar effect was observed after treatment of R. solani with Bacillus spp. ( Montealegre et al., 2003 and Yangui et al., 2008). However, no publications have demonstrated the induction of these detrimental effects in R. solani hyphae by B. pumilus.