The authors applied seven different sets of diagnostic criteria for alcoholism to data obtained by using the Schedule of Affective Disorders and Schizophrenia (SADS) in a community sample. They found that the different diagnostic schemes for alcoholism are hierarchical in the sense that some definitions identify smaller groups of subjects as alcoholic than do other definitions. This study illustrates a potentially useful empirical approach to comparing diagnostic criteria for psychiatric disorders in epidemiologic or clinical studies.