SUMMARY/ABSTRACT Youth and young adulthood are critical periods for tobacco use. For most of the past two decades, smoking has steadily declined among young people in the US and other Western countries, including Canada (CA) and England (EN). In contrast, nicotine vaping products (NVPs) have experienced rapid growth and are now the most prevalent nicotine product used by youth and young adults. The long-term public health impact of NVP use among young people is widely debated, including its impact on smoking behavior as either a `gateway' into smoking or a means to `displace' cigarette use. The nicotine market is poised to diversify further with the emergence of heated tobacco products (HTPs), such as Marlboro Heatsticks in the US, and novel oral nicotine products. The extent to which these novel products appeal to young people and follow a similar trajectory as NVPs represents a critical question. The policy environment is changing in response to the rapidly evolving product market. A range of new nicotine and tobacco policies are in the process of being implemented in the US, CA and EN, most of which are targeted at reducing use among young people. The different regulatory approaches across countries creates a series of `natural experiments' in nicotine and tobacco policy, which can be used to evaluate their impact on young people. The proposed study consists of repeated cross-sectional surveys conducted annually with national samples of youth and young adults (aged 16-29) in the US, CA and EN. The same methods and measures are used in all three countries to provide directly comparable estimates over time. The study would expand the current focus of the International Tobacco Control Policy Evaluation Project (ITC) Youth surveys to include young adults (20-29) and will build on the four annual surveys waves conducted between 2017 and 2020. The study has three primary aims: 1) to examine international variations in smoking, NVP, and HTP use among young people; 2) to examine the impact of national-level policies on prevalence and patterns of smoking and vaping among young people; and 3) to examine the relative impact of policies on youth versus adult smokers. Overall, the proposed Project is uniquely positioned to examine changes in tobacco and nicotine use among young people during a critical period in which both the product and policy landscape is rapidly evolving. The between-country design provides a unique framework for assessing the impact of specific policies, as well as the emergence of novel HTPs and oral nicotine products. Finally, Project 2 is well-positioned to examine broader contextual differences across countries, such as the legalization of cannabis.