Purpose : To evaluate the mammographic and clinical findings of nonpalpable breast cancer. Materials andMethods : In 28 of 607 breast cancer patients examined between January 1994 and April 1997, lesions werenonpalpable. We retrospectively analyzed the mammographic, clinical and pathologic features of 25 patients (28lesions) whose mammograms we obtained. Results : Among these 25 patients (28 lesions) screening was abnormal in22; other symptoms were bloody nipple discharge(n=4), and nipple eczema(n=2). The patients were 34-62 (mean 52)years old. Invasive ductal carcinoma(n=13), DCIS(ductal carcinoma in situ, n-12), Paget's disease (n=2), andLCIS(lobular carcinoma in situ, n=1) were found during surgery. Six of 28 lesions(21%) showed evidence of axillarynodal metastasis;the majority arose from the upper outer quadrant of the breast (n=21). The mammographic findingswere mass (50%), (and mass with microcalcification, 11%); microcalcification(29%); asymmetrical density(14%); andnormal (7%). According to the mammographic density of breast parenchyma, the major finding in the low densitygroup(N1+P1) was mas (9/9), and in the high density group(P2+DY) was microcalcification (12/19). Conclusion : Themost common mammographic findings of nonpable breast cancer were mass (50%) and microcalcification(29%). Itsfeatures varied according to the mammographic density of breast parenchyma;mass was the main finding in the lowdensity group and microcalcification in the high density group.