The influence of nitrogen and phosphate sources on the production of extracellular protease activity by Streptomyces clavuligerus has been investigated. The experiments were carried out in batch fermentation using soy-bean flour as nitrogen source and potassium phosphate dibasic as phosphate source. High protease yield was obtained after 24 h of fermentation with an initial pH of 7.0. The maximal protease activity (112.68 and 88.72 U/mg) was obtained the phosphate concentration of the 21 and 29 mM for strains 3585 and 644, respectively. With regard to the nitrogen concentration in both strains, the maximal protease activity was achieved with 0.5% (154.89 U/mg and 228.36 U/mg for 3585 and 644 strains, respectively). Enzyme production appeared to be modulated by an inducer system where ammonia, complex nitrogen, and phosphate sources might have been involved.