The occurrence of organic storage compounds in six strains of sulfate-reducing bacteria was investigated. In Desulfovibrio HL21 and Desulfovibrio vulgaris NCIB 8303 accumulation of polyglucose was brought about by limiting the Fe2+ or NH4+ concentration in the growth medium. Desulfobulbus propionicus 1pr3 and especially Desulfovibrio gigas NCIB 9332 already synthesized large amounts of polyglucose in normal media, whereas the synthesis of polyglucose in two strains of Desulfovibrio desulfuricans was far less pronounced. Suspensions of Desulfovibrio HL21 cells in media without an energy source and sulfate degraded the polyglucose to acetate, hydrogen and small amounts of ethanol and succinate; Desulfobulbus propionicus formed acetate, propionate and some hydrogen under these conditions. In the presence of sulfate both strains produced acetate and corresponding amounts of sulfide. None of the strains synthesized PHB as a storage polymer.