The NCTM's Research Committee has prepared this article as a means to raise the awareness about equity and issues surrounding equity from a research perspective as well as to support the NCTM's commitment to the Equity Principle. The committee discusses the concept of equity from three perspectives: as a subject of research, as a "critical lens" with which to examine research, and as a cross-disciplinary theme. Equity issues offer a unique opportunity to unite research and practice within mathematics education and across other disciplines. (Contains 2 footnotes.)