Background: Delays in breast cancer diagnosis may occur in young women due to a low index of suspicion. The purpose of this study was to compare mammography and breast sonography in detection of breast cancer and to suggest a reasonable guideline for breast cancer screening examination. Materials and Methods: Among 820 patients, 102 patients were under 35 years and 122 patients were above 60 years of age. We reviewed medical records, mammograms and/or ultrasonography of 49 patients under 35 years and 48 patients above 60 years of age with pathologically-proven breast cancer. Pathological reports were as follows Invasive ductal carcinoma(IDC) was present 61.2% of patients in the young age group and ductal carcinoma in situ(DCIS) in 16.3%. IDC was present in 66.6% of the patients in the old age group, and DCIS in 8.33%. We analyzed mammography and ultrasonography to evaluate their usefulness in detecting breast cancer in patients under 35 years and over 60 years of age. Results: The mammographic results are as follows : 1) detection rate of lesion: 83.8%(under 35yrs), 100%(over 60yrs) 2) sensitivity of cancer: 67.6%(under 35yrs), 91.2%(over 60yrs) The ultrasonographic results are as follows : 1) detection rate of lesion: 100% 2) sensitivity of cancer: 87.2%(under 35yrs), 96.7%(over 60yrs) The breast cancer detection rate in women under 35 years old was comparable to that of women above 60 years old in our study. Conclusion: A striking histologic finding in the two groups was a higher incidence of nuclear Grade II and III tumors. This finding correlates with the reported increased incidence of high grade tumors in young women and may correlate with the poorer prognosis of breast cancer in young patients. We conclude that early screening examination is helpful for early detection of breast cancer in women under age 35.