Publisher Summary Behavioral changes in humans are exposed to highly toxic organophosphorus (OP) compounds, called nerve agents. The incidence of behavioral effects is higher in individuals who have been severely exposed to nerve agents, but they may occur in individuals who have received a small exposure and have no or minimal physical signs and symptoms. The behavioral effects usually start within a few hours and last from several days to several weeks or months. The most frequent symptoms include feelings of uneasiness, tenseness, and fatigue. Exposed individuals may be forgetful and generally display impaired memory and learning, poor comprehension, decreased ability to communicate, or occasional mild confusion. There are a few reports that described behavioral changes in subjects accidentally exposed to nerve agents. The report stated sleep disturbance, mood changes, fatigue, jitteriness or tenseness, an inability to read with comprehension, difficulties with thinking and expression, forgetfulness, a feeling of being mentally slowed, depression, irritability, giddiness, poor performance in arithmetic tests, minor difficulties in orientation, and frightening dreams. It was observed that the complex of central nervous system (CNS) symptoms may not fully develop until 24 h after exposure. In addition, no correlations between the presence or severity of symptoms and the degree of acetylcholinesterase inhibition were seen. Most of the effects of exposure disappear within 3 days. It was concluded that not only severe but also mild intoxication of nerve agents might cause behavioral and psychological disturbances. In general, the behavioral effects have not been permanent but have lasted from weeks to several months, or possibly several years.