Ninety-three patients with neurological manifestations and suspected exogenous intoxication were analysed. The detection of toxic substances was performed in the blood, urine and cerebrospinal fluid. There was clear predominance of the central nervous system impairment than the peripheric, and an apparent tropism of herbicides and organophosphates to the central nervous system compared with the peripheral nervous system, and considering the manifestations caused by carbamates and organochlorines. The authors analyse some probable action mechanism of these substances in the nervous system, and show the most frequently neurological signs and symptoms found.