On May 17, 2004, Massachusetts became the first state to legalize same-gender marriage. From California to Missouri, nearly all states now face legislative challenges to the once firmly entrenched notion that marriage can only exist between a man and a woman. Public opinion polls conducted from 1977 to 2004 found that Americans' attitudes toward gay men and lesbians and marriages or civil unions for same-gender couples have evolved. Opposition persists, however. The most recent data indicate support for some legal recognition of gay and lesbian couples, but most Americans favor civil unions over same-gender marriages. Although the future of civil unions and same-gender marriages remains uncertain, social workers can serve gay and lesbian clients and their families best by staying informed of the attendant legal, social, and policy issues.