This paper presents results from a study which examined the occurrence and time course of smoking withdrawal symptoms in a group of 33 smokers followed over a 21 day period of abstinence. Smoking withdrawal symptoms examined included: irritability, feeling sleepy, sleeplessness, dizziness, coughing, tightness in the chest, constipation, mouth sores, and cravings for a cigarette. Findings showed a fairly consistent pattern of reduction across days of abstinence for six of the nine symptoms examined--irritability, feeling sleepy, dizziness, coughing, tightness in the chest, and cravings. Most symptoms decreased sharply during the first few days of cessation followed by a continued, but slower rate of decline in the second and third week of abstinence. Heavy smokers tended to report more withdrawal symptoms than light smokers, although the difference between heavy and light smokers was statistically significant only with respect to irritability. The implications of these findings for relapse prevention are discussed.