This study examined the situational factors leading to relapse in a group of 69 smokers who quit and returned to smoking during a 1-year period following participation in a stop smoking clinic. Two-thirds of relapses occurred in the first 3 months after quitting, with the largest percentage (13/47 = 40%) occurring in the first week following cessation. Results showed that the circumstances leading to relapse varied as a function of the amount of time off of cigarettes. Among subjects relapsing in the first week after quitting, withdrawal symptoms and craving a cigarette was the most frequently cited reason for relapse. After the first week of cessation, coping with crisis situations and exposure to certain smoking triggers, such as the presence of other smokers and consumption of alcohol and coffee, were the main reasons given for relapse. The findings from this study suggest that pharmacologic influences associated with withdrawal from nicotine play an important role in early relapse, while psychosocial aspects of the smoking habit (i.e., coping with stress, other smokers) are the main causes of later relapse. The implications of these findings for relapse prevention are discussed.