NOVELTY - Predicting natural damping capacity of a contaminant, involves supplying a sustained release electron donor to the to be process target e.g. soil or underground water, proliferating microorganisms having ability to decompose the contaminant, detecting the microorganisms by detecting target gene sequence contained in the microorganisms, and estimating natural damping capacity of contaminant by detecting presence or absence of microorganisms.    USE - (M1) is useful for predicting natural damping capacity of a contaminant, preferably chlorinated organic compound (claimed) e.g. trichloroethylene, 1,1,2-trichloroethane, carbon tetrachloride, chloroform and dichloromethane.    ADVANTAGE - (M1) enables reliable and accurate estimation of the decomposition ability of a contaminant (natural damping capacity of contaminant) in soil or underground water.    DETAILED DESCRIPTION - Predicting (M1) natural damping capacity of a contaminant, involves supplying a sustained release electron donor to the to be process target such as soil or underground water, proliferating microorganisms or microorganisms group having the ability to decompose the contaminant contained in the to be process target, detecting the microorganisms by detecting the target specific gene sequence contained in the microorganisms, and determining or estimating the natural damping capacity of the contaminant by detecting the presence or absence of the microorganisms.    An INDEPENDENT CLAIM is included for a method for predicting natural attenuation, involves supplying many kinds of electron donor in the process of (M1), and specifying the optimal electron donor for the proliferation of the microorganisms.    DESCRIPTION OF DRAWING(S) - The figure shows sectional drawing the underground water (process target) on which the natural damping capacity prediction method is performed. (Drawing includes non-English language text).    hydrogen supply agent (13)    H+ (14)    injection well for the hydrogen supply agent (15)