42 commercial peptones were tested for use in media to be employed in obtaining fluorescence with Pseudomonas fiuorescens and closely allied organisms. Peptones varied greatly in composition and suitability for pigment production. Some lacked sufficient amounts of the different necessary constituents; one may lack phosphate, another magnesium, etc. Each peptone should be tested before use. A 0.5% peptone broth is more satisfactory for pigment production than is a 3% broth. Purines, meat bases, and asparagine do not stimulate the power of pigment production in peptones. Heating peptone broth for a reasonable time under pressure does not destroy the power to produce fluorescence.