For the experimental studies on chronic coronary stenosis, an ameroid constrictor was modified to facilitate serial cineangiographic evaluation of the degree of arterial narrowing. A radiolucent plastic ring instead of a stainless frame was used to prevent outward swelling of the ameroid material. Coronary cineangiography was performed 10, 20 and 30 days after the implantation of the modified ameroid constrictor on the left circumflex coronary artery (LCX), which could prove the progressive coronary stenosis of 57, 78 and 88% on the respective days. Collateral channels from the anterior descending branch of the left coronary artery to the LCX were demonstrated angiographically in 5 out of the 6 dogs on the 30th day.