Transdermal nicotine delivery systems are a cigarette smoking cessation aid designed to deliver nicotine into the systemic circulation via the skin. The partial replacement of plasma nicotine, which would have otherwise been obtained from cigarettes, reduces the severity of nicotine withdrawal symptoms, and so allows the smoker to abstain from smoking more easily. The systems are available in 16- and 24-hour application regimens, and are recommended for daily use for up to 20 weeks, including a series of 'weaning-off' courses. Clinical trials have shown that abstinence rates of 30 to 41% can be achieved during the first 6 weeks of application of transdermal nicotine systems, compared with 4 to 21% with placebo systems. The use of concomitant behavioural therapy may increase the success of treatment, with initial abstinence rates of up to 86% reported. However, long term abstinence rates (greater than 6 months) are considerably lower with or without behavioural therapy, often falling to less than half of the initial rates. Transdermal nicotine systems have been well tolerated in clinical trials, with local irritation at the site of application being the most common adverse event. Mild gastric, central nervous system (CNS) and sleep disturbances have also been reported. The ease of use and unobtrusive nature of the systems have resulted in a high degree of patient compliance. Thus, transdermal nicotine systems offer a convenient form of nicotine replacement therapy which are well tolerated and, due to their pharmacokinetic profile, probably have a low dependency potential. The short term abstinence rates achieved with this therapy are encouraging; however, the maintenance of abstinence in the long term is harder to achieve. Transdermal nicotine replacement therapy, therefore, represents an important advance in the difficult area of smoking cessation management.