The accurate measurement of radial expansive force is crucial for optimal design and implantation of self expandable esophageal metal stents. In the present study, a new method of measurement under experimental conditions simulating actual stent implantation has been developed. This method offers precise and reproducible measurements and can be applied to a wide variety of stent types. In particular, the method enables one to measure expansive pressure as well as the true radial expansive force up to the radial compression ratio of 72%, covering the range of compression often encountered in a partially obstructed lumen. The test results for various kinds of metal stents are presented and compared. Based on these results, three important points of observation critical in explaining and predicting the expansion characteristics of stents have been reported. Further understanding and characterization of these findings will be necessary for developing new stents with outstanding clinical efficacy.