Eight hundred forty-three smokers were referred to the smoking cessation service from January 2000 to December 2002. Of these, 600 smokers were excluded due to exclusion criteria, being unable to be contacted for further intervention, or saturation of staff resources due to large referral numbers during busy periods. The remaining 243 smokers were recruited into the study. Twenty-seven of these subjects were excluded after enrolment due to inadequate attendance of the smoking cessation program (ie, they did not complete an initial visit plus two follow-up visits or phone contacts). Therefore, a total of 216 subjects who completed the smoking cessation program were evaluated; 187 never-smoker subjects were recruited as control subjects.