· Background: The purpose of this study was to measure the activity of the sympathetic nervous system in patients with central serous chorioretinopathy (CSC) by power spectral analysis (PSA) of heart-rate (RR-interval) variability, a noninvasive method that reflects the balance of the sympathetic-vagal interaction. · Methods: The following four different groups of patients were measured: group 1, acute CSC (n=11); group 2, acute recurrent CSC (n=7); group 3, chronic persistent CSC (n=4); group 4, complete remission of CSC (n=9). The data recorded for these 31 patients (29 men and 2 women), with an average age of 44 years were compared with those noted for a group of 15 age-matched healthy individuals. The sympathetic-vagal balance is expressed by the ratio of the low-frequency component (LF) to the high-frequency component (HF) of the power spectrum. · Results: Significant differences in mean LF/HF ratios were found as follows for all but one of the subgroups as compared with the normal controls (LF/HF=1.1): group 1, LF/HF=5.5 (P<0.01); group 2, LF/HF=5,4 (P<0.05); group 3, LF/HF=4.2 (P=0.1); and group 4, LF/HF=3.0 (P<0.01). There was also a significant difference between active CSC and inactive CSC (P<0.05). · Conclusions: These results support the view that the pathogenesis of CSC is related to an increase in the sympathetic activity of the autonomic nervous system. Furthermore, the LF/HF ratios seem to correlate with the activity of the disease.