The authors propose phenomenological criteria for a diagnostic entity, "As-If Personality Disorder." These are: (1) apparent normality; (2) shifting identifications; (3) lack of affect; (4) easy substitution of one relationship for another; (5) absence of social isolation; and (6) preservation of reality testing. In addition, such patients may also exhibit simulated affect, extensive imitation of others, moral plasticity, and lack of insight. They suffer from depressive syndromes only rarely; they may report feelings of emptiness or emotional deadness. The differential diagnosis of the As-If Personality Disorder includes schizoid personality, the borderline syndromes, and normal adolescence, in which as-if phenomena are frequently observed. There are three brief case presentations which illustrate the application of these criteria in the psychiatric evaluation.