A fundamental prerequisite for the design of neurotoxicological safety studies is the determination of the target areas in the nervous system which are specific for particular kinds of toxicants. The target areas should be identified in special "lesion-pattern-finding" experiments. The pyridoxine-induced lesion is a prototype of the pattern characteristic of a peripheral, primary sensory neuropathy. Depending on the conditions of treatment such as the dosage level and the timing of examination, the structural changes may be more obvious either in the proximal or the distal portion of the neuron, while the functional signs may vary from severe sensory paralysis to quite unremarkable behavior.