The carotid sinus baroreflex is one of the most important negative feedback systems to stabilize arterial pressure. Although static characteristics of the carotid sinus baroreflex can be assessed by using a stepwise input protocol under baroreflex open-loop conditions, the step duration has been determined empirically. In the present study, we examined the effects of different time windows (5-10, 15-20, 25-30, 35-40, 45-50, and 55-60 s) on the static characteristics estimated by using a 60-s stepwise input protocol in 10 anesthetized rats. Based on the results, we compared the static characteristics between actual 60-s and 20-s stepwise input protocols. Most of the parameters of the static characteristics did not differ significantly between the 60-s and 20-s stepwise input protocols, suggesting that the open-loop baroreflex static characteristics can be estimated by using a stepwise input with the step duration as short as 20 s in normal rats.