Smoking is the greatest avoidable cause of premature death in Britain today, particularly among the poorest people in society. Most smokers take up the habit during childhood, and the age at which children begin to smoke is falling over time. Although patterns of regular smoking are often established during the teenage years, rates of experimentation with cigarettes peak during preadolescence. Despite this, in the UK there has been little longitudinal research into the process of smoking uptake during preadolescence, and this research fills that significant gap. The Liverpool Longitudinal Study of Smoking (LLSS) is a unique longitudinal study that has tracked a cohort of approximately 250 children during their early years at primary school. This thesis continues and develops the LLSS by exploring the cohort's experiences of smoking during preadolescence in order to understand how children's early smoking careers develop between the ages of 9 and 11. Baseline quantitative and qualitative data collected at age 9 (in 1999) were compared with data collected at age 10 (in 2000) and at age 11 (in 2001) in order to identify key elements of change. These data were analysed longitudinally using a multiple case study approach that identified the individual trajectories of five children during preadolescence. A cross-case comparative method was then used to identify and explain the relationship between views, intentions and behaviour, and how these were shaped by the social context in which the children lived. The themes that emerged from the case studies were then explored and developed in the context of data generated by the whole cohort. Statistical analysis revealed that smoking by best friends, fathers and brothers, together with knowing someone with a smoking-related disease, at age 9 predicted smoking by age 11. The discourses that the children used to talk about smoking uptake emphasised the role of parents at age 9, but by age 11 the cohort suggested that friends were the key influence on smoking onset. Each year, anxiety about being bullied into smoking by older children also emerged as a key concern for this age group. In addition, the analysis revealed that preadolescents appropriate adult discourses around the use of smoking as a coping strategy. The use of these discourses was patterned by socioeconomic status. Children who lived in deprived areas suggested that both adults and children might smoke to counter stress and to relieve boredom. However, some of the girls living in relatively affluent areas perceived that adults smoke to control their weight. The study also considered the implications of these discourses for differential rates of smoking uptake at primary school. A key finding of this phase of the LLSS is that preadolescents construct smoking as an adult behaviour, and therefore some children smoke in order to negotiate status in anticipation of the transition to adolescence and as a strategy of resistance to the exercise of adult power. The reduction of rates of smoking among children and young people is central to the government's tobacco control strategy, and this research has significant implications for the development of both interventions and policy.