The Symposium on Metrology and Standards for Cell Signaling: Impact on Tissue Engineering, was cosponsored by the National Institute for Standards and Technology (NIST) and ASTM International, and was held at the NIST on October 14 and 15, 2003. The purpose of the symposium was to discuss the role of standards and quantitative measurements of cellular responses for the field of tissue engineering. Accurate and quantitative measurements, reference materials, and standards are needed to facilitate the understanding and control of cell responses to materials, culture media, and the in vivo environment. Speakers included government researchers from the NIST, the Food and Drug Administration, and the National Cancer Institute; vice presidents, chief executive officers, and directors of research from companies; and academic researchers in engineering, medicine, and cell biology. The metrology needs identified include quantitative assays of cell signaling pathways, bioinformatics that will allow consolidation of these complex data and permit correlative parameters to be identified, well-characterized standardized cell lines against which responses in other cells can be compared, and reference materials for use in control experiments.