The baroreflex is a sympatho inhibitory reflex being a major determinant of sympatho-vagal balance. Despite the impaired baroreflex control of heart rate (HR) and increased renal sympathetic activity (RSNA), observed in patients and animals with heart failure (HF), the gain of the arterial baroreceptor reflex control of RSNA can be found preserved in this cardiovascular disease (1,2,3). The sequence method is an approach that assesses spontaneous beat-to-beat arterial pressure (AP) fluctuations and their related HR changes. The sequence method has never been applied to assess baroreflex control of RSNA. We propose the use of the sequence method for analysis of spontaneous baroreflex function, using AP and RSNA signals, as an alternative approach to spectral methods. We analyzed the baroreflex gain by the barocurve, cross spectral analysis and sequence method in control (n=7) and rats with HF induced by myocardial infarction (n=6). The experimental protocol was approved by the Committee of Ethics in Animal Research of the School of Medicine of Ribeirao Preto, Brazil (Protocol n. 1477/2007). Rats were anesthetized with ketamine (50mg/kg,ip) and xylazine (10mg/kg,ip) and underwent surgery to implant stainless steel electrodes around the renal nerve and catheters into the femoral artery and vein for AP recording and phenylephrine and sodium nitroprusside administration. Barocurves were calculated fitting systolic AP vs RSNA curves by sigmoidal regression. The spectral method applied estimates the gain of the transfer function in the high frequency band, considering AP as the input and RSNA as the output of a linear time-invariant system. The sequence method identifies successive spontaneous increases or decreases (ramps) in AP that produces efferent responses in RSNA (sequences). The gain is the averaged slope, obtained from all sequences found. Baroreflex effectiveness index (BEI) is the ratio between baroreflex sequences and the number of AP ramps, taken as the percentage of AP ramps that are actually producing a reflex response by baroreflex. All methods employed to assess the baroreflex gain (%RNSA/mmHg), barocurve (1.78±0.4 vs 1.63±0.2 HF rats), transfer function (14.6±4.7 vs 15.2±1.5 HF rats) and sequence method (17.1±6.9 vs 22.1±2.4 HF rats) did not detect any difference between control and HF group. However, HF rats showed lower BEI (0.6±0.02 vs 0.3±0.04 HF rats, p<0.05). It means that, when the baroreflex is acting, its sensibility is similar in control and HF animals. Nevertheless, its effectiveness to buffer changes in the efferent pathway is markedly affected in HF. In conclusion, these data demonstrated that while the gain of the baroreflex could not reveal any difference between control and HF rats, BEI is markedly decreased in HF rats, indicating attenuated baroreflex effectiveness to buffer changes in RSNA in HF rats.