The objective of this longitudinal (3 year) study was to determine predictors of abstinence in 515 employees of a steel plant (28% female, age 18-67 years) after participation in Allen Carr seminars (intensive group counselling in a single session of 6 h). Answers given in computer aided phone interviews were analysed by stepwise and Cox regression. Of 510 responding persons 262 (51.4%) reported continuing abstinence. In a random sample of 61 respondents cotinine concentration in urine was measured, showing high agreement with smoking history. Social support increased abstinence, which was more persistent in males and office workers. Also in female participants the non-smoking spouse was a significant predictor for abstinence while a higher body weight predicted relapse. Relapsed female smokers did not show a sustainable reduction of cigarette consumption. Compared to cessation clinics higher population coverage would be achievable by workplace seminars. Every second smoker motivated to participate seems to be able to quit even without medication and to stay abstinent. Especially in females these seminars should be followed by physical exercise and continued support of gender specific occupational health care.