The impact of spinal anesthesia on cardiac rhythm variability was studied in 36 children aged 13-17 years who had been operated on for urological, orthopedic, and vascular diseases. The findings were compared with the results obtained in 83 children with the same pathology at the age of 7-15 years, who had been operated under general anesthesia. A spectral cardiac sinus rhythm analysis demonstrated a steady state of stress-limiting systems during spinal block. Unlike general anesthesia, spinal anesthesia was ascertained to reduce the likelihood of intraoperative arrhythmias, by producing an adequate analgesic effect.