At 6 P.M. the nightmare begins: You're holding your 2-week-old baby when she stiffens her limbs, arches her back, clenches her fists, draws her legs up against a bloated belly, and emits the first in a long series of ear-piercing shrieks. As the intensity of her cries mounts, so does your frustration. She's inconsolable, and soon you're both in tears. You cuddle her, but she goes rigid in protest; you try to nurse, but she pulls away; you rock and sing, but the soothing techniques that worked yesterday aren't working today. Inside your head, the familiar refrain plays over and over again: "What's wrong with my baby; what's wrong with me?"

Months later, when you've gone through the herbal teas, the dietary changes, and every conceivable comforting measure, the onslaught ends as mysteriously as it began, and you close one of the most difficult chapters of life with your new baby. That's colic.

Dr. William Sears is a contributing editor of BabyTalk and coauthor with his wife, Martha Sears, of Parenting the Fussy Baby and High-Need Child (Little, Brown).