PURPOSE: Contralateral reduction mammaplasty at the time of breast reconstruction using autogenous tissue gives aesthetically improved results in the patients with mammary hypertrophy or ptosis. It also reduces required flap size for reconstruction and permits discarding zones of poor perfusion, decreasing flap size- related problems such as partial flap loss or fat necrosis. Considering the high rate of bilaterality of breast cancer, it also provides a good opportunity for exploration and occult cancer diagnosis in such high risk group patients. METHODS: We retrospectively reviewed 45 consecutive patients who underwent simultaneous breast reconstruction and contralateral reduction mammaplasty was performed about surgical technique, pathologic diagnosis, and subsequent treatment. RESULTS: Three occult breast cancers were found in 45 patients(6.7%); one was microinvasive, and the other two were invasive carcinomas and their mean diameter was 1.2 cm. One patient underwent subsequent breast conserving mastectomy, adjuvant radiation and chemotherapy. The others underwent only radiation and hormone therapy. They were followed up for 10 to 42 months without evidence of recurrence or metastasis. CONCLUSION: Occult breast cancer diagnosed in reduction mammaplasty specimen will lead to good prognosis due to its early detection. Treatment options depend on pathologic finding, stage, marginal status, and the timing of diagnosis. We recommend adequate markings for orientation and margins, excision with sufficient margin, and confirmation by frozen biopsy for suspected lesions.