The purpose of this investigation was to determine whether the observation of Ferenczi and Purves-Stewart that conversion reactions occur with higher frequency on the left side of the body than on the right side could be confirmed. Both right-handed and left-handed patients experienced a higher proportion of left-sided symptoms (weakness or paralysis; sensory loss or numbness) than would be expected by chance, indicating a lack of support for the hypothesis that unilateral conversion symptoms occur most frequently on the most "convenient" (nondominant) side of the body. These findings and prior reports of left-sided lateralization of psychogenic pain were interpreted as support for the hypothesis that the right cerebral hemisphere is particularly involved in the mediation of affectively or motivationally determined somatic symptoms. The question of a possible link between these results and certain symptoms of disease of the right hemisphere was raised.