To compare the advantages of one-view vs two-view mammography screening, films were reviewed for 2500 consecutive asymptomatic women undergoing baseline mammography. To provide screening at low cost, examinations were limited to two radiographs per breast, one each in the craniocaudal and mediolateral oblique projections, with the understanding that those few patients with detected abnormalities would require additional mammograms, taken with an individually directed, problem-solving approach, at considerably higher cost. Two separate interpretations were made of each case, one using only the oblique projection images, the other using both oblique and craniocaudal views. Two-view interpretations not only identified more cancers than one-view readings (27 vs 25), they also required fewer additional mammograms to evaluate potential abnormalities (179 vs 642, 7% vs 26%). These advantages outweigh the additional radiation risk and added cost. Baseline screening mammography should be done with two views per breast.