The neuropathic effects of triphenyl phosphite (TTP), a widely used industrial and agricultural organophosphorus compound, were examined in the present study. Long-Evans, male rats were exposed (sc) to either single (0.1ml/kg; 1.0ml/kg) or multiple (2 x 1.0 ml/kg; 2 x 1.0ml/kg) doses of TPP and sampled 7-21 d post-exposure. Functional changes, seen in multiple-dosed rats included tail-kinking, circling, and ataxia. Neuropathologic changes, seen in all but 1x 0.1 ml/kg treated group, predominantly involved the spinal cord and brainstem. Degeneration was largely confined to the lateral and ventral columns of the spinal cord, with moderate degeneration noted in Rexed laminae VI, VII, IX. Medullary degeneration was seen in the medial longitudinal fasciculus, the medial vestibular nucleus, the inferior cerebellar peduncle, and the reticular formation. Moderate peripheral nerve fiber involvement consisted of wallerian-like degeneration, and dorsal root ganglion necrosis. These data indicate that the neuropathic profile of TPP differs markedly from the delayed neuropathy (OPIDN) associated with exposure to organophosphorus compounds.