Defines a procedure for the evaluation in aqueous medium of the ultimate biodegradability and as information, the primary biodegradability and the total elimination from water, of organic compounds at a specified concentration by aerobic microorganisms. The procedure is applicable to organic compounds which are water-soluble at the concentration used under the test conditions and not expected to be transformed to insoluble metabolites if biodegradation; nonvolatile, or which have negligible vapour pressure under test conditions; not lost by foaming from the test solution and not inhibitory to the microorganisms at the concentration chosen for the test.