Image-based examination of the breast facilitates the detection of breast diseases, particularly of present benign and malignant lesions. For computer-aided processing of serial and multimodal clinical data, both for visual correlation and quantitative analysis, automated image-registration methods are an indispensable tool. The wide range of modalities and the high variability of breast appearance have led to a large diversity of proposed approaches for tissue deformation modeling and image registration. In this article, we review current developments in breast image registration techniques, and comment on their clinical relevance, individual capabilities, and open challenges.