PURPOSE: Fat necrosis is a well-described and relatively common complication arising from post-lumpectomy irradiation of the breast, most commonly breast brachytherapy. We wish to assess the clinical significance of fat necrosis resulting from post-lumpectomy breast irradiation. METHODS: We reviewed the literature to determine the overall incidence and significance of fat necrosis to determine whether or not fat necrosis poses a significant clinical problem. RESULTS: Fat necrosis occurs in up to one-quarter of patients following post-lumpectomy breast irradiation. Only rarely is invasive intervention required however, it does significantly degrade the quality of all modalities of breast imaging. CONCLUSIONS: Fat necrosis is a common complication of radiotherapy which rarely requires therapeutic intervention. However, post-therapeutic clinical imaging such as mammography, ultrasound and magnetic resonance imaging are affected which may result in additional diagnostic procedures up to and including biopsy.