SUMMARYAutonomic nervous dysfunction has been previously reported in SLE, RA and systemic sclerosis, but the pathogenesis of such a complication is poorly understood. In the present study, four standard cardiovascular autonomic function tests were performed in 34 female patients with connective tissue diseases and in 25 healthy control subjects, and results expressed as cardiovascular (CV) test scores. Moreover, in each subject the presence of circulating complement-fixing autoantibodies directed against sympathetic and parasympathetic nervous structures, represented by superior cervical ganglia and vagus nerve, respectively, was simultaneously assessed by an indirect immunofluorescent complement-fixation technique, using rabbit tissue as substrate. None of the patients reported autonomic symptoms. However, an abnormal CV test score (Ն 5) was detected in 15% of the patients and in none of the healthy control subjects, approaching statistical significance (P ¼ 0·07). No correlation was found between CV test results and disease duration, type of therapy or presence of conventional autoantibodies. One or two autoantibodies to autonomic nervous structures were detected in six patients (18%) and not in the control subjects (P < 0·05). Values of deep breathing test were significantly lower in autoantibody-positive patients compared with those amongst the control subjects (P < 0·05), and an abnormal CV test score was significantly associated with the presence of autoantibodies to autonomic nervous structures (P < 0·05). In conclusion, we confirm that autonomic nervous function can be impaired in patients with connective tissue diseases, and suggest that autoantibodies directed against autonomic nervous system structures may play a role in the pathogenesis of the autonomic dysfunction.