This study will recruit 200 smokers who report little change to their enjoyment of cigarettes and no nausea, during the first week of varenicline use. These smokers will be randomised to receive the standard dose plus placebo or plus individualised varenicline dose up to 5mg, titrated over the next week prior to their target quit day. Urges to smoke, and other withdrawal symptoms, experienced during the study period will be compared between groups to see if the tailored therapy may be useful.