In this study, R-R interval variation (RRIV) and sympathetic skin response (SSR) were used to evaluate autonomic nervous system (ANS) involvement in 25 patients with Behçet's disease. Normative values of RRIV and SSR were determined in a group of 25 healthy volunteers. R-R interval variation at rest (R%) and during deep breathing (D%), the difference between D% and R% (D-R), and the ratio of D% to R% (D/R) were determined. R-R interval variations did not show a significant difference between patients and the control group. There was a negative correlation with age for R%, D%, and D-R in the control group, but none was found in the patient group. The SSR latencies were two standard deviations above the normal mean values in three patients who described symptoms of autonomic dysfunction. In conclusion, symptoms of autonomic disturbance must be evaluated carefully for a possible involvement of ANS that might occur in Behçet's disease.