The Thrombolysis in myocardial infarction (TIMI) frame count is a simple clinical tool for assessing quantitative indexes of coronary blood flow. This measurement has been significantly correlated with flow velocity measured with a flow-wire by several investigators during baseline conditions or hyperemia. In this study we aimed to evaluate the coronary flow in patients with isolated coronary artery ectasia by means of the TIMI frame count and to compare the results with those of patients with angiographically normal coronary arteries. The study population consisted of 37 patients with coronary artery ectasia only in the right coronary artery (RCA). The control group consisted of 31 patients with angiographically proven normal coronary arteries. Coronary artery ectasia was defined as nonobstructive lesions of the coronary arteries with a luminal dilatation 1.5-fold or more of the adjacent normal coronary segments. The TIMI frame count was determined for each major coronary artery in each patient according to the methods first described by Gibson et al. The TIMI frame count of RCA in the study group was significantly higher than in that of the control group (51+/-17 vs 25+/-8, P<0.0001). The TIMI frame counts of the study group for the left anterior descending and left circumflex coronary artery were also significantly higher than those of the control group (corrected TIMI frame count for LAD=42+/-11 vs 24+/-7, P<0.001; TIMI frame count for LCx=44+/-15 vs 25+/-9, P<0.001). In patients with coronary artery ectasia, the TIMI frame count of the RCA was higher than that of the left anterior descending and left circumflex coronary artery (51+/-17 vs 42+/-11 and 44+/-15, respectively, P<0.05). We have shown increased TIMI frame counts in patients with isolated coronary artery ectasia and suggest that the pathophysiological mechanism of coronary artery ectasia is not a focal disease. TIMI frame counts can be regarded as an index of the severity of impaired coronary flow in patients with coronary artery ectasia.