Objective: The aim of this study was to evaluate angiographic changes in the ulnar and interosseous arteries, and the collateral circulation of forehand after harvesting radial artery. Methods: Forty patients were studied between June 1998 and June 2001. Study group consisted of 30 patients who received radial artery as a conduit for coronary artery bypass operation, and control group consisted of 10 patients who did not undergo any cardiac or vascular operation before. Preoperative risk factors were similar between the two groups. All patients underwent angiographic evaluation to detect coronary artery and left forehand arterial circulation. Results: Angiographic evaluation was performed 25.5 ± 2.0 months after the initial operation in the study group. Mean diameter of ulnar artery was 2.9 ± 0.59 mm (range 2.1 - 4.8) in the study group and 3.2 ± 0.8 mm (range 1.5 t- 4.7) in the control group (p > 0.05). Mean diameter of interosseous artery was significantly higher in the study group than in control one: 2.06 ± 0.57 mm (range 1.2 t- 4.2) versus 1.46 ± 0.79 mm (range 0.8 t- 3.6); (p = 0.003). Conclusion: Although angiography was performed in a limited number of patients, interosseous artery rather than ulnar artery enlarged to compensate blood supply of forehand 25 months after harvesting the radial artery for coronary artery bypass grafting.