We studied the relationship between the contrast characteristics of barium suspension and timing of exposure. We poured several kinds of barium preparations on the phantom manufactured by ourselves, and took X-ray pictures continuously by a DSA system. We analyzed each of the characteris-tics of the contrast. The time which was reguired for the contrast to reach the peak (Contrast Peak Time ; CPT) was unrelated with the kind of barium preparations used. It depended on the viscosity of the contrast media and the angle of the phantom. Viscosity was correlated with CPT. CPT was 3 to 6 seconds at an angle of 15 degrees, and 1.5 to 4 seconds at an angle of 30 degrees. We can refer to these findings to decide the density of barium suspension and to get timely exposure.