A medium for the production of the phenazine pigment pyocyanine by Pseudomonas aeruginosa has been developed. The medium was deficient in phosphate and contained ammonium chloride, inorganic salts, and 2-ketogluconate as sole carbon source. Rapid initiation of pigment formation was observed with synthesis being completed at 24 h. Kinetics of growth, substrate concentration, pigment elaboration, and phosphate liberation have been examined. In the presence of excess nitrogen pigment concentration was proportional to the level of 2-ketogluconate used.