There is conflicting evidence concerning gender differences in success at quitting smoking. Information is especially lacking regarding gender differences among unaided quitters who make up the vast majority of those attempting to quit. One hundred thirty-five smokers who made an unaided attempt at quitting were interviewed before quitting and were followed for 1 year after cessation. Relapse rates were extremely high both for men and women, with 62% of participants returning to regular smoking within 15 days after cessation. Women and men were equally likely to maintain short-term abstinence (through 15 days), but women were more than three times as likely to relapse subsequently. Nine percent of men, but no women, had biochemically verified sustained abstinence throughout the 1-year follow-up period. For both men and women, any smoking after the quit attempt inevitably led to full-blown relapse. Most participants resumed regular smoking within 24 hours after the first episode of smoking. Gender differences were observed for several variables related to smoking history, demographics, social support, perceived stress, and motivational factors, but these differences did not explain the increased risk of relapse for women. Our results clearly indicate that women are less likely than men to maintain long-term smoking abstinence following an unaided quit attempt, but reasons for this gender difference need further exploration.