The effects of inorganic salts, inoculum concentration, aeration rate and shaking speed on insoluble phosphate solubilization by Pseudomonas fluorescens RAF15 were investigated. Soluble phosphate production was dependent on the presence of MgCl₂·6H₂O and MgSO₄·7H₂O in the medium. Supplementation of medium with 0.01% CaCl₂·2H₂O and 0.01% NaCl slightly increased soluble phosphate production. The optimal medium compositions for the solubilization of insoluble phosphate by P. fluorescens RAF15 were 1.5% glucose, 0.005% urea, 0.3% MgCl₂·6H₂O, 0.01% MgSO₄·7H₂O, 0.01% CaCl₂·2H₂O and 0.01% NaCl, respectively. Optimal inoculum concentration was 2.0%(v/v). Maximum soluble phosphate production was obtained with 20-50 ml/250-ml flask and 200 rpm of shaking speed, respectively. The addition of EDTA decreased cell growth and soluble phosphate production.