The patient was tall, with legs that extended to the very end of the operating table, a chest barely wider than his 16-year-old hips and a chin covered with pimples and peach fuzz. He looked like any number of boys I knew in high school, I reflected. And then the other transplant surgeons and I began the operation to remove the dead boy's liver, kidneys, pancreas, lungs and heart. The boy had hanged himself. He had been discovered early, though not early enough to have survived. Until recently, there has been little attention among health care professionals to this particular form of youthful thrill-seeking. What has been known, however, is that those ages 7 to 21 participate in such activities alone or in groups, holding their breath, strangling one another or dangling in a noose in the hopes of attaining a legal high. (Illustration by Katherine Streeter/The New York Times) **ONLY FOR USE WITH STORY BY PAULINE W. CHEN SLUGGED: SCI-CHOKING-GAME. ALL OTHER USE PROHIBITED. EDITORIAL USE ONLY