Habit is defined as a firmly established behavior pattern marked by increasing automaticity, decreasing awareness, and partial independence from reinforcement. Reinforcement is viewed as of primary importance in the acquisition of behavior, whereas principles of associative learning enter to complement reinforcement in the maintenance of behavior. Habit is seen as a mechanism for short-circuiting the reinforcement process to avoid its overload and for providing the organism with speed and stability of response instead of the variability offered by reinforcement. The implications of this definition of habit for acquisition and alteration of health behavior are discussed; examples include smoking, obesity, alcoholism, and coronary-prone (type A) behavior.