A workshop was sponsored by the National Institute of Standards and Technology, the Cancer Diagnosis Program of the National Cancer Institute, the Food and Drug Administration, and the College of American Pathologists to address the need for a reference material for Her2 gene protein testing. It was agreed that such a standard was desirable and necessary to ensure the reliability of Her2 testing to qualify patients for trastuzumab therapy. Two standards consisting of well characterized cell lines will be produced, 1 that will be a National Institute of Standards and Technology-certifiable standard, and 1 that will be a commercially developed standard for use in all Her2 testing. It was also agreed that all Her2 testing must be performed on samples fixed only in 10% buffered formalin, as specified in the Food and Drug Administration-approved testing methods. Participants agreed to plan strategies to educate pathologists, clinicians, and laboratories about the need and use of such a standard. A National Committee for Clinical Laboratory Standards guideline for the use of the standard reference material will be created to facilitate this process.