This review of the recent literature on personality disorders summarizes theoretical and methodologic issues, DSM-III-R criteria sets, nosological controversies, and current treatment approaches. Work in the personality disorders is burgeoning, with increasing attention to improved reliability and validity of diagnosis. Investigators are looking at such issues as the development of dimensional taxonomies, the effect of state variables, the problem of diagnostic overlap, the effect of comorbid conditions on course and treatment, the predictive power of criteria, and external validators. The DSM-III-R criteria sets, despite their polythetic format, may be no more reliable than their predecessors. Because treatment remains largely unresearched, the dinician must continue to rely on skillful assessment of each patient, with psychoanalytic psychotherapy and symptom-oriented drug trials providing the foundation of therapy.