The urges to smoke reported by 215 former smokers were measured 1 day, 7 days, 14 days and 30 days after they quit to examine: (a) the time course of smoking urges, (b) the relationship of urges to relapse, and (c) predictors of urges to smoke. Urges to smoke were strongest 1 day after quitting, and decreased at each subsequent measurement point. Urges were a powerful predictor of relapse. At each of the four assessment points, abstinent subjects who reported stronger urges to smoke were more likely to relapse by the next measurement point. Urges to smoke at a given day (e.g., day 1) were consistently the best predictors of the persistence of urges at the next assessment (e.g., day 7). Greater negative emotion (e.g., anxiety, sadness, anger, and confusion) and psychosocial stress also predicted stronger urges to smoke. Nicotine gum significantly reduced urges during week 1 post-cessation. Clinical implications of the findings are discussed.