The addition of various catecholamines to cultures of gram negative bacteria resulted in dramatic increases in growth. The ability of norepinephrine, epinephrine, dopamine and dopa to enhance the growth of Escherichia coli, Yersinia enterocolitica and Pseudomonas aeruginosa was observed to be dependent on the bacterium employed with each strain showing marked preference for one or more of the catecholamines. Catecholamine induced increases in growth were confirmed by one or more of the following methods: uptake of tritiated thymidine into newly synthesized DNA, changes in optical density or pour plate analysis. None of the catecholamine metabolites resulting from either oxidative deamination or catechol-O-methylation were able to effect similar increases in bacterial growth as compared to either norepinephrine, epinephrine or dopamine. Norepinephrine was consistently observed to effect the greatest increase in bacterial growth for all strains tested.