A highly important function of the nervous system (NS) is to process the information arriving to us from external, environmental sources. This capacity may be discontinued by chemicals restricting the plasticity of the NS, disturbing its adaptability to the ever changing environment. NS and endocrine system are profoundly bound together, changes, disruption of the different regulatory endocrine levels by toxicants may take part in the development of manyfold neural disfunction. The various endocrine levels (integrative, modulatory, regulatory, effector, target gland, etc.) affecting neurotoxicity and affected by neurotoxicity are discussed. The NS is protected against some toxic insults but is rather sensitive to other ones. By electrophysiological and psychophysiological methods, used as sensitive biomarkers the signs of functional disturbances of the NS can be proved both in human investigations and in animal experiments at an early stage of low concentration intoxications when clinical or general laboratory symptoms do not indicate yet the moderate poisoning.