Twenty-one patients (mean age 68 +/- 8 years) with dual-sensor (QT+activity) DDDR pacemaker were randomly assigned to a crossover, double-blind study in order to evaluate their quality-of-life scores. All pacemakers were implanted for sick sinus syndrome (8 patients) or complete heart block (13 patients). The pacemakers were randomly programmed to VVIR or DDD pacing modes for 2-week periods and then the pacing mode was switched for another 2-week period. At the end of each period, the quality-of-life was evaluated by a questionnaire with regard to cardiovascular symptoms, physical activity, psychosocial and emotional functioning, and self-perceived health. Nineteen questions were scored 0-5 points each. Significant improvement in the mean total quality-of-life score (20.5 +/- 14.9 vs 34.8 +/- 17.4) as well as in dyspnea on effort, dizzy spells, palpitation, sweating, fatigue, lethargy, emotional functioning, and self-perceived health was observed during DDD compared to VVIR pacing. No question was scored in favor of VVIR pacing mode. Significant improvements during DDD pacing was demonstrated in all subgroups of patients (sick sinus syndrome, chronotropically competent and incompetent patients, and patients with high degree AV block). Eighteen patients preferred DDD pacing mode, while only one preferred VVIR pacing mode. Two remaining patients expressed no preference. The results suggest that DDD pacing offers better quality-of-life than dual sensor VVIR pacing in all subgroups of patients commonly indicated for pacemaker implantation.