Selective and differentiating media consisting of simple chemical components have been developed, both in solid and in liquid form, for culturing Pseudomonas aeruginosa from foodstuffs. These media work on the basic principle that Gram-negative bacteria can utilize ammonia as inorganic nitrogen source. This principle has already been utilized for developing a culture medium for coliform bacteria (Szita and Biró, 1986; Szita et al., 1988). P. aeruginosa can produce the ammonia needed for its growth by decomposing acetamide. The liquid synthetic medium was compared with the nitrofurantoin broth and the solid one with cetrimide agar by parallel inoculation of 60 raw milk samples and 20 P. aeruginosa pure cultures. The main advantages of the synthetic media are their high selectivity, high sensitivity and rapidity. Owing to their advantageous properties, the new media can be recommended for replacing cetrimide agar and nitrofurantoin broth.