Nervous system involvement is rare in progressive systemic sclerosis (PSS). We present a clinical pathological and immunological study of two patients with peripheral sensory motor neuropathy and PSS. In both, the sural nerve biopsies showed axonal degeneration with increased endoneurial connective tissue. There were also clusters of myelinated fibres indicating axonal regeneration. Only mild microangiopathic changes were evident in the endo, peri and epineurial vessels. By Western immunoblots, patients' sera contained a band of reactivity to a protein from peripheral nerve identified as collagen type I. Primary involvement of the peripheral nerves during PSS is very unusual. Abnormal production of collagen tissue and presence of microvascular disease are considered to be two possible causes of neuropathy. We think that our results suggest the important role of the connective tissue proliferation in the pathogenesis of PSS neuropathy.