Identification of creep damage variable D of continuum damage theory from the metallographical A-parameter is discussed. By preforming a stochastic analysis, A-parameter defined as the observed fraction of cavitated grain boundaries on the observation plane was first related to the cavity area fraction on the gain boundary facet planes. Based on the results of this analysis, the cavitation damage states of some engineering alloys were estimated by use of data of the measured A-parameter. Finally, according to the usual interpretation of the damage variable D, specific D-A relations were derived. The validity and the utility of the proposed D-A relations were discussed based on the test results of an engineering alloy.