A prospective study in 47 patients was undertaken to determine which of the two major sites for injection of contrast material, superior vena cava or antecubital vein, produces digital subtraction images of higher quality. Both injection sites were used to obtain images of the carotid and aortic arch areas in each patient. The two injection sites were also compared for ease of performance of the study, patient acceptance, and incidence of complications and motion artifacts. It was determined that the degree of vessel conspicuity is not affected by injection site when equal volumes of contrast material are injected. No significant differences in overall image quality attributable to injection site were found, except for carotid images obtained in the anteroposterior projection; for these images, the antecubital vein injection site produced significantly better images. Vessel conspicuity was not the major determinant of overall image quality as judged by radiologists.