"The National Association of Social Workers (NASW) is the largest membership organization of professional social workers in the world, with 150,000 members. NASW works to enhance the professional growth and development of its members, to create and maintain professional standards, and to advance sound social policies." (http://www.naswdc.org). Social workers adhere to the NASW Code of Ethics which serves as a guide for professional practice.
There are NASW Chapters in all fifty states and several international sites.