Sympathetic skin response (SSR), a non-invasive method for evaluation of the autonomic nervous system, was studied in 57 patients with various connective tissue disorders: scleroderma, dermatomyositis, polymyositis, scleromyositis and unclassified collagenoses. The patients were divided into three main groups: scleroderma (SSc), myositis or other inflammatory myopathy (M) and scleromyositis (ScM). The aim of the study was to detect abnormalities of the SSR in the connective tissue diseases, to define the pattern for each group and to evaluate the usefulness of SSR in detection of subclinical impairment of sympathetic cholinergic function. In the myositis group, an abnormal SSR was found in 88% of patients; the main abnormality was absence of the response from the lower limbs (in 50% of patients). In scleroderma, the SSR was abnormal in 77% of patients, consisting mainly of absence of the response from the lower limbs, whereas responses from the upper limbs were normal. In scleromyositis, the SSR was abnormal in 80% of patients, the most frequent finding was an increase in latency in one limb. The SSR changes were most pronounced in connective tissue disorders with myositis or inflammatory myopathy. The SSR, although non-disease-specific, because of its sensitivity, seems to be useful in the assessment of the abnormalities of the autonomic nervous system in scleroderma and inflammatory myopathies. The study showed a very high prevalence of autonomic nervous system dysfunction in connective tissue diseases associated with myopathy or myositis, displaying no clinical symptoms of autonomic system involvement.