BACKGROUND: Evaluation of changes in breast shape, particularly "upper pole fullness," "breast projection," and "bottoming out," has been made difficult by the lack of an accepted definition of these entities and no standardized system for measurements and comparison. Three-dimensional imaging is impractical for most surgeons and limited in providing evidence-based assessments. METHODS: Using standardized photographs and computer imaging software to match size and orientation, breast shape and size are measured and compared before and after cosmetic breast surgery. Practical landmarks and analysis allow assessment of results using standard two-dimensional frontal and lateral views. A horizontal plane at the level of maximum postoperative breast projection and a vertical plane dropped from the sternal notch serve as the reference planes. Breast projection, upper pole projection, lower pole level, nipple level, lower pole width, breast parenchymal ratio, and lower pole ratio (a measure of the boxiness of the lower pole) are defined and measured. RESULTS: These simple measurements may be easily used by surgeons to evaluate the effectiveness of their techniques in breast augmentation, mastopexy, augmentation/mastopexy, and reduction. Claims regarding changes in breast projection, upper pole projection, and breast mound elevation may be objectively evaluated. CONCLUSION: This measurement system provides a highly practical means with which to quantitate breast shape changes after surgery and assess surgical results using well-defined references. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.