Although traditionally seen as disparate clinical entities, primitive personalities and organic personalities share many diagnostic and therapeutic characteristics. Both involve disruptions in the core self-system, and both require corrective-educative psychotherapeutic techniques, in addition to more interpretive ones. A previously well-adjusted personality may be rendered somewhat more “primitive” by brain damage, while an impulsive, emotionally labile, nonreflective primitive personality may place himself or herself at increased risk for acquired injury to an already-vulnerable brain. Suggestions for evaluation and treatment of these patients are offered.