AIMS: High-frequency paced breathing is required to avoid overestimation when measuring spectral baroreflex sensitivity (BRSLF) to predict outcomes in cardiovascular patients. We examined whether respiration should also be controlled when measuring the baroreflex effectiveness index (BEI) and baroreflex sensitivity (BRSseq), which are derived by sequence analysis. METHODS: We studied 17 healthy young adults who breathed spontaneously and controlled their breathing to rates of 0.1, 0.2, 0.3 and 0.4 Hz in the supine position. We found respiratory influences on BEI and BRSseq depended on the lag used to pair the systolic arterial pressure and R-R interval in a sequence. Therefore, the two baroreflex measures were obtained by selecting the lag with a larger number of sequences for each section. RESULTS: BEI decreased progressively as the breathing frequency increased. BRSseq remained unchanged at rates of 0.1, 0.2 and 0.3 Hz, but was reduced during 0.4 Hz breathing. In contrast, BRSLF was constant during 0.2, 0.3, and 0.4 Hz breathing, but was greater at 0.1 Hz. Rates of spontaneous breathing range from 0.1 to 0.32 Hz with a mean value of 0.19 Hz. Baroreflex measures obtained for spontaneous breathing were found to be between the values for 0.1 and 0.3 Hz paced breathing. CONCLUSION: BEI and BRSseq do not remain constant at various breathing frequencies. Nonetheless, considering the pattern of change and the frequency range of spontaneous respiration, the authors suggest that high-frequency paced breathing is not necessary when measuring the BEI and BRSseq under the conditions used in this study.