Polyacrylamides (PAMs) are xenobiotic polymers consisting of covalently linked carbon atoms (-CH2-CH2), unlike the an-hydro bonds of many biological polymers. Although the carbon chains are resistant to microbial breakdown, field observations by people in the oil industry support the notion that polyacrylamides can somehow stimulate the growth of microorganisms. This paper presents data indicating that PAMs can provide nitrogen (as ammonia) for several species ofPseudomonasisolated from soil. Growth in a defined medium can be sustained over several transfers in a chemically defined medium with no added NH4Cl. The level of growth attained was less (∼25–50%) than that with NH4Cl. No change in the viscoelastic property (screen factor) of the PAM occurred. Growth of sulfate-reducing bacteria is also stimulated by polyacrylamides, with a loss of screen factor of the polymer solution accompanying the growth. To some extent this is because the polymer serves as a nitrogen source, but another factor, in the case of SRBs, is the ability of the polymer to serve as an incomplete substrate (mixotrophic growth)