Myocardial fibrosis causes the fragmentation of QRS complexes (fQRS) on ECGs. We hypothesized that the frequency of fQRS could be more common in patients with rheumatoid arthritis (RA) than in control subjects. A total of 56 patients with RA were compared with 35 age- and gender-matched fibromyalgia subjects for fQRS. The fQRS was defined as the presence of an additional R wave, or notching of the R or S wave, or the presence of fragmentation in 2 contiguous leads corresponding to the territory of a major coronary artery. Patients with bundle block on ECG and cardiovascular disease were excluded. Twenty-one patients (37.5%) in the RA group had fQRS, while two patients in the control group (5.7%) had fQRS (p = 0.001). No differences were found between the groups in terms of age, gender, or drug use. Duration of disease--years (interquartile range [IQR])--was 10 (8) in the fQRS (+) group, while it was 5 (2) in the fQRS (-) group (p < 0.001). Multivariate logistic regression analysis revealed that duration of disease was associated with the presence of fQRS (B = 1.5, odds ratio = 4.5, p = 0.004, 95% confidence interval = 1.6-12.7). We found that fQRS on ECG was more common in patients with RA without cardiovascular disease than in age- and gender-matched control subjects.