PURPOSE: This study is to describe authors'experience on mammographic findings of breast cancer and to know if there is difference between 35 years of age or younger and older groups. MATERIALS AND METHODS: Mammograms of 72 patients with breast cancer detected from January, 1991 to December, 1993 were retrospectively analysed. Mammographic findings were classified into mass only, mass with microcalcifications, microcalcifications only and others. Marginal characteristics of mass were classified into spiculated, poorly marginated and well marginated. Shape of microcalcifications were classified into casting, granular and mixed types. These findings were compared between 35 years of age or younger and older groups. RESULTS: Mammogram showed mass only in 33 patients(46%), mass with microcalcifications in 26 patients (36%), microcalcifications only in seven(10%) and other findings in six(8%). Other findings were architectural distortion, asymmetric high density and incidental breart carcinoma from paraffinoma in one patient respectively, and dense breast in three patients. The margins of the breast mass were spiculated in ten(17%) poorly marginated in 30(51%), well-marginated in 19(32%). Shape of microcalcifications were casting type in 13(40%), granular in 14(42%) and mixed in six(18%) cases. 3 patients had dense breast with which mammography did not demonstrate the lesion. 3 patients without mammographically demonstrable lesions due to dense breasts were under 35 years in age. and there was statistically significant difference between the two groups(p-value<0.05). Microcalcifications only was more common findings in 35 years of age or younger. CONCLUSION: The most important mammographic findings of breast cancer were mass and microcalcifications. Architectural distortion and asymmetric high density were additional findings. In 35 years of age or younger, microcalcifications only was an important finding because mass lesions are frequently masked by dense breast. Thus other imaging modalities, such as ultrasonography, were required.