OBJECTIVES: To assess item analysis and dimensional validity of a new questionnaire developed to measure Satisfaction with medical care in patients with atrial fibrillation, in order to accomplish item reduction. METHODS: The initial instrument was composed by 37 items, arranged in 6 dimensions: 1- Efficacy (4 items), 2- Ease and convenience (7 items), 3- Impact on daily activities (11 items), 4- Satisfaction with medical care (6 items), 5- Medication undesired effects (6 items), and 6- Overall satisfaction (4 items). Items and dimensions where extracted from reviewing previous English instruments, 3 focus groups with chronic patients, and a panel composed by 8 experts. Additionally 3 Visual Analog Scales (VAS) measuring Quality of Life, Effectiveness and Overall Satisfaction were applied. A convenience sample of 118 patients was used. Classic psychometric theory item analysis techniques, exploratory factor and confirmatory factor analysis, test-retest and correlation with VAS scales were used. RESULTS: The questionnaire was reduced in length to 25 items, but the Impact dimension had to be divided in 2 dimensions: Treatment inconvenience and Treatment Control. The reduced version presents an overall Cronbach alpha of 0.861, with acceptable dimensional reliabilities (0.764-0.908). Individual dimensions were well formed and correlated in different degrees, being the dimension of Satisfaction with medical care the most independent one. Test-retest correlations were high (0.784-0.965) and correlations with VAS scales were meaningful. CONCLUSIONS: The 25-item questionnaire shows good reliability and validity to assess satisfaction with medical care in patients with atrial fibrillation. Further research is needed to examine if the questionnaire could be generalized to different populations of patients with atrial fibrillation.