Behavioral toxicology is an emerging field which is becoming increasingly important in risk assessment of exposure to neurotoxic substances, due to the high sensitivity of behavior towards neurotoxic action and the integration in behavioral functions of several underlying processes and neurofunctions, such as motor, sensory, attention, motivational. Whenever it is difficult to isolate the relative contribution of sensory, motor, arousal, or cognitive factors that contribute to an observed behavioral change, possible mechanism of behavioral alteration may rely on the involvement of neurotransmitters, such as the dopaminergic system and catecholamines metabolism. Examples are given of different behavioral types of changes induced in humans by organic solvents (styrene), metals (manganese) and anaesthetic gases, based on a possible common underlying mechanism of toxicity.