The bill would prohibit workplace discrimination against gay, bisexual and transgender Americans.
Seated at a desk, Kirk said it was especially important for an Illinois Republican to speak out for the legislation in the tradition of Everett Dirksen and Abraham Lincoln. Kirk hadn't taken the Senate floor since suffering a stroke in January 2012.
Federal law prohibits discrimination on the basis of sex, race and national origin. But it doesn't stop an employer from firing or refusing to hire workers because they are gay, lesbian, bisexual or transgender.
All of the Senate Democratic majority and at least five Republicans are expected to vote for the bill.