Cytisine is a natural product found in plants such as Golden Rain and New Zealand Kowhai that partially blocks the effects of nicotine on the brain. Cytisine has been used as a smoking cessation treatment in several European countries since the 1960s, is inexpensive compared to other cessation medications and has few known side effects. Despite its long history of use there are few studies looking at whether cytisine actually works but they suggest that taking cytisine almost doubles the chances of successfully quitting smoking, compared to a placebo. However, these studies were not conducted using modern research standards so their positive findings may not be valid. We propose to investigate the effectiveness of cytisine as a quit smoking aid and whether it is safe and acceptable to smokers.