SUMMARY: Mutants of Pseudomonas aeruginosa 8602 were isolated which were unable to grow with acetamide as sole carbon source. They were divided into five classes on the basis of growth studies and enzyme assays. The mutants able to grow on acetate but not acetamide (Am–) lacked an inducible amidase. Mutants unable to utilize either acetamide or acetate (At–) lacked one of the glyoxylate cycle enzymes (isocitrate lyase or malate synthase) or were deficient in citrate synthase or acetic thiokinase. Isocitrate lyase-negative mutants grew on propionate which is therefore not metabolized by the glyoxylate cycle. The amidase marker was not co-transduced with the isocitrate lyase, acetic thiokinase or citrate synthase markers.