Part 1 of 2. A report on prostitution in the U.S. surveys the world's oldest profession, from legal Nevada brothels and high-end Manhattan call-girl rings to streetwalking in Philadelphia. Interviewees include New York Times columnist Nicholas Kristof. Diane Sawyer is the correspondent.

Included: a report on the August 2006 shooting of a white teenager following a misunderstanding with a black classmate in the New York City suburb of Miller Place, Long Island. The father of the black teen was charged in the killing. Also: John Stossel on the rights of smokers and nonsmokers.

Included: consumer advice. Also: a preview of the April National Geographic Channel documentary "Human Footprint," which explores how much of the world's resources an average American consumes in a lifetime.