Fluorescent pseudomonads have been widely tested for their ability to promote plant growth and to suppress soilborne diseases. Their efficacy is both related to their activity and to their density in the rhizosphere. To enable the introduction of a number of bacterial cells high enough to allow the expression of their beneficial activities, the strain must be produced at a low cost. In order to optimise the inoculum production of the biocontrol agent Pseudomonas fluorescens C7R12, different combinations of carbon, nitrogen and yeast extract including the reference King's B medium (KB) were compared using a central composite design. Among the different growing media tested with P. fluorescens C7R12, 6 gave a high rate of growth for this strain and for several other bacterial strains. The carbon and nitrogen concentrations of these 6 media were a lot lower than those used KB medium and their nitrogen sources were a lot cheaper. However, these 6 media supported a growth non significantly different from KB medium.