Many factors (pathological subtype differences, etiology, clinical practice, etc.) may cause ethnic sensitivities in drugs. For drugs approved in one region, their differences among ethnic groups and the potential impacts of such differences on their safety and efficacy must be explained before seeking approvals in another region. Despite potential ethnic sensitivities, if pharmaceutical companies are required to repeat the clinical research and development process in various countries, it will result in waste of resources and delays in drug approval. To address this issue, the International Conference on Harmonization (ICH) published a guideline entitled , known as ICH E5, in 1998. With an attempt to offer guidance on the monitoring and research & development (R&D) of innovation drugs, the concept of bridging studies was for the first proposed, which allows the adequate assessment of ethnic differences in safety, efficacy, dosage, or dose regimen of an innovation drug, and meanwhile minimizes the duplication of clinical data in two different regions to speed up the licensing of the drug in the new region. Here we take breast cancer as an example to describe the concept, types, strategies, statistical methods, and clinical practice of bridging studies, focusing on their development in China.