We have developed the phased tracking method for measuring the minute change in thickness during one heart-beat and the elasticity of the arterial wall. By comparing the pathological findings with the elasticity distribution measured with ultrasound, statistic parameters for respective tissues in the arterial wall were determined. We have already measured the statistic parameters for lipid and a mixture of smooth muscle and collagen fiber. In this paper, elasticity distributions were measured for blood clot and calcined tissue. Then, we discussed whether the measured elasticity distributions can be used as reference data for classifying cross-sectional elasticity images. In addition to the measurement of elasticity distribution, the correlation between the collagen content and the elasticity was investigated for fibrous tissue. Collagen is supposed to mainly contribute to the stability of the fibrous cap of atherosclerotic plaque. Therefore, such a correlation between elasticity and a tissue element of the wall may provide useful information on diagnosis of plaque vulnerability.