Objective: During the course of acute rheumatic fever, some electrocardiographic changes are seen. First-degree atrioventricular block is the most common electrocardiographic abnormality. Second- and third-degree atrioventricular block, ventricular tachycardia, and junctional acceleration are also seen. In the present study, the specificity of accelerated junctional rhythm to acute rheumatic fever was investigated. Methods: The study included patients with acute rheumatic fever (Group 1), healthy children who had suffered from recent group A β-haemolytic streptococcal upper respiratory tract infection but did not develop acute rheumatic fever (Group 2), and patients who had other diseases that may affect the joints and/or heart (Group 3). Results: Accelerated junctional rhythm was detected in 10 patients in Group 1, but in none of the patients from Group 2 or 3. Specificity of accelerated junctional rhythm for acute rheumatic fever was 100% and the positive predictive value was 100%. Conclusion: Accelerated junctional rhythm is specific to acute rheumatic fever. Although its frequency is low, it seems that it can be used in the differential diagnosis of acute rheumatic fever, especially in patients with isolated polyarthritis.