Activity rate response programming depends on the physician’s experience and on the limited knowledge of patient’s daily activities. The present investigation compares a new continuous automatic adjustment of the activity rate response called rate response optimization (OPT) with fixed activity rate response programming (FIXED). At hospital discharge 37 patients with Thera DR pacemakers (Medtronic) were randomized either to FIXED (n = 20; 65 ± 12 years, male n = 12) or to OPT (n = 17; 65 ± 12 years, male n = 13). After 1 month’s follow-up occurrence of complaints related to rate-responsive pacing and the percentage of pacing were assessed. Other activity sensor parameters were programmed according to clinical judgement and similarly distributed in the two groups. Activity rate response was 7.1 ± 1.4 (FIXED) and 7.2 ± 1.7 (OPT), activity threshold was medium in 9 (FIXED) and 8 (OPT), and medium/low in 11 (FIXED) and 9 (OPT) patients, respectively. No patient with FIXED had any complaints with respect to activity-triggered rate response. One patient with OPT reported palpitations due to rapid changes in the pacing rate leading to reprogramming of the pacemaker. Atrium and ventricle were paced in 56 ± 31% (FIXED) and in 58 ± 35% (OPT; not significant) and the atrium only in 4 ± 10% (FIXED) and 0% (OPT; not significant), respectively. In the 17 patients programmed to OPT the pacemaker increased activity rate response in 5 and decreased activity rate response in 3 patients. In conclusion, as only 1 (3%) patient had complaints related to the activity rate response and fixed rate response programming according to clinical judgement already resulting in symptom-free DDDR pacing, no differences could be detected between the fixed rate response programming and rate response optimization.