To evaluate if the 0.1-Hz low-frequency oscillations of R-R interval are a reflection of rhythmical pattern of discharge of the sympathetic outflow, we analysed in 10 decerebrate cats heart rate and cardiac sympathetic efferent discharge variability. A predominant low-frequency component was present in both signals, thus suggesting that the 0.1-Hz rhythm indeed reflects a rhythmical pattern of discharge of sympathetic outflow.