This book presents the rationale, principles, and evidence for the effectiveness of harm reduction strategies in minimising tobacco use and its consequences, as well as summarising implications for public health policy and clinical practice. Combustible tobacco smoking is a major determinant of population health, as it contributes significantly to all-cause morbidity and mortality. The most common causes of death from smoking are malignant neoplasms and cardiovascular and respiratory diseases, which together account for more than 90% of all smoking-related deaths. In high-income countries, smoking is responsible for up to 10% of healthcare costs. Smokers are likely to die up to ten years earlier than non-smokers, and for every person who dies, as many as thirty live with a serious disease attributable to tobacco smoke. However, traditional strategies and tools have not yielded satisfactory reductions in the prevalence of smoking at both the individual and population levels. Rather than nicotine, the main drivers of smoking-related morbidity and mortality are the irritant, toxic, and carcinogenic compounds of tobacco smoke.Smoking-specific harm reduction strategies involve using nicotine in less harmful forms. For example, nicotine replacement therapy, which has long been available, follows this principle. However, new opportunities have arisen from alternative consumer products, such as electronic cigarettes, heated tobacco products, or nicotine pouches. These alternatives are much less harmful than smoking, with the health risks posed by some of them being comparable to those of nicotine replacement therapy. 
The best available evidence indicates that alternative products do not serve as a gateway to smoking; rather, they divert smokers from conventional cigarettes and replace smoking among individuals with a higher predisposition to experimentation with nicotine who would otherwise have taken up smoking. Alternative products have also been shown to be effective in smoking cessation and can play a role in counselling in clinical settings as a substitute for smoking in individuals who cannot or do not wish to quit nicotine use. In this way, alternative products complement traditional cessation methods and represent an opportunity that may be decisive in addressing the smoking epidemic and its consequences.