The coolest heads keep warm by never forgetting their hats. According to Dr. Murray Hamlet, who directs the Cold Research Division of the U.S. Army Research Institute of Environmental Medicine in Natick, Mass., insulating the head keeps the whole body warmer: "Your mother told you if your hands are cold, put your hat on -- and it is true." Hats are especially effective for older people who want to keep warm indoors, he points out.

"You lose a significant amount of heat through your head," says Hamlet. "Blood flow to your hands and feet is under neurologic control, whereas blood flow to your head is solely dependent on the amount of blood your heart puts out; if you are exercising, more blood goes to your head, and you can lose more heat through your head," adds Hamlet.

Pictured below are the freshest hotheads around. CAPTION: Pictures 1 through 5, kelly green beret by Jean-Charles Brosseau for Jean-Claude de Luca ($75) and wool shawl by Kenzo ($50), both at La Boutique Francaise. hand-knit aviator hat by Cigany ($140) at Dolly Kay, Ltd. Swedish army hat ($16.50) at Hudson Trail Outfitters. Brown wool Chitrali from Pakistan ($18), alpaca ragg mittens ($19) and plaid alpaca scarf ($28), all at Pavo Real. "Fanciful Blue Fish" hat by Diana Willner ($90) at Jackie Chalkley; red scarf ($42) at I. Magnin, Makeup by Gary Longwood of Elizabeth Arden. Models: Holly O'Dell, Jennifer Zeichman and Wayde Warner. PHOTOGRAPHS BY LUCIAN PERKINS