Personality changes in 7 participants with bilateral ventromedial prefrontal lesions (PF-BVM), 14 participants with prefrontal lesions but not bilateral ventromedial involvement (PF-NBVM), and 36 with nonprefrontal lesions (NPF) were investigated with the Iowa Rating Scales of Personality Change. Informants rated 30 specific characteristics for degree of disturbance and change from premorbid personality. PF-BVM participants showed a higher rate of acquired disturbances than NPF participants in blunted emotional experience, apathy, low emotional expressiveness, inappropriate affect, poor frustration tolerance, irritability, lability, indecisiveness, poor judgment, social inappropriateness, lack of planning, lack of initiation and persistence, and lack of insight. Differences between the PF-BVM and PF-NBVM groups were significant for several of these characteristics. All 7 PF-BVM participants developed a syndrome, including general dampening of emotional experience; poorly modulated emotional reactions; defective decision making, especially in the social realm; impaired goal-directed behavior; and striking lack of insight. Similarities between this syndrome of "acquired sociopathy" and developmental psychopathy in characteristic personality disturbances and psychophysiological abnormalities suggest that diminished emotionality, impaired decision making, and psychosocial dysfunction may be related to ventromedial prefrontal dysfunction in both groups.