Fourteen individuals briefly exposed to a toxic industrial compound, pentaborane, were evaluated for neuropsychiatric abnormalities four to 12 weeks after exposure. Results of physical, neurological, and routine laboratory evaluations were normal. Initial and persistent psychiatric symptoms, neuropsychological deficits, electroencephalographic changes, elevated central nervous system neurotransmitter levels, and ventricular brain ratios (computed tomographic scan) provide evidence of central nervous system damage. Seven patients met diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders, ed 3, for posttraumatic stress disorder, and seven patients had neuropsychological test evidence of mild brain dysfunction. No statistically significant relationship was found between neuropsychiatric test results and psychiatric diagnoses. These results contradict previous literature that reports most symptom resolution within the first week after exposure to pentaborane. Results suggest that patients suffered a combination of organic brain insult and psychological trauma.