Tabulation of cases reported in the literature of unilateral psychogenic somatic symptoms revealed that more symptoms were on the left side of the body than on the right; this result, although falling short of statistical significance, is consistent with recent reviews of hospital records by Stern and by Galin et al. A review of organic diseases and traumata for which lateral preferences have been reported, and a retrospective study of hospital emergency room records, provided no evidence for the hypothesis that the left-sided predominance of psychogenic symptoms is underlain by a generalized greater vulnerability of the left side to organic pathologies. The status of three other explanations for the asymmetrical incidence of psychogenic symptoms is discussed.Both clinical observation and systematic investigation have suggested that, when unilateral, somatic complaints with arguably psychogenic components are more frequent on the left than on the right. Such a gradient has been reported for hysterical hemianesthesia (21), hypochondriasis (45), "rheumatic" and "neuritic" complaints (19,36,37), pain in psychiatric patients (1, 89), and postamputational stump pain (61). Most recently, careful reviews of hospital records by Stern (90) and by Galin et al. (27) have found unilateral conversion symptoms to occur more often on the left than on the right. (A report by Fallik and Sigal [20] provides an exception to the directional gradients found in the studies just cited; of their 33 unilateral cases, 76 per cent had rightsided symptoms.)At least three varieties of explanation for a left-sided predominance of psychogenic symptoms have been proposed. The first assumes that-probably because most humans are right-handed-the symbolic or evaluative significance of right and left are different. Malevolent forces are sinister; physically or socially clumsy persons are maladroit or gauche; skilled motor performances require manual dexterity; unintended or grudging praise is expressed in left-handed compliments; the mind of the wise man faces right, but the mind of the fool faces left (Eccl. 10:2). Given a psychological association between right and good, and between left and evil, one might expect the neurotic choice of symptom site to be influenced by such associations. This ____________________________ A second explanation has been called the convenience hypothesis (90). On the assumption of a variant of the law of least effort, the (right-handed_ neurotic in search of a symptom site would find it less discommoding to have, say, a paralyzed left arm than a paralyzed right arm. This hypothesis predicts that left-handers should have more rightsided stigmata. However, of eight sinistrals with unilateral sensory conversion symptoms, Stern (90) found that seven had their symptoms on the left, and of six with unilateral motor symptoms, all had left side involvement. Analysis by body part 2 makes the argument still more compelling. All eight of the sensory symptom cases, and five of the six motor symptom cases, were patients with i...