Testicular self-examination (TSE) is an important behaviour to prevent the development of testicular cancer. This thesis examined the stages of decision making, emotions, perceived costs and benefits of screening, the self perceptions, social influences, and health routines in samples of adult males and adolescent school boys. A multi-method approach was adopted involving qualitative and quantitative methods of study. The qualitative part of the investigation comprised a series of studies including focus groups, in-depth interviews, programme evaluation and survey studies. The aim was to elucidate the meanings associated with health and illness and preventive cancer screening. Such information formed the bases for developing a survey measure and a health promotion programme to promote TSE. A comparative cross-sectional approach, including the components of three social cognition models was then carried out revealing a hybrid model (HSCM) to be most effective in explaining TSE. Acknowledging traditional social cognitions as predictors of TSE decision making, it also stresses the importance of emotional cognitions, self perceptions and routine behaviours. Using a five-stage model building approach, a longitudinal examination of stages of decision making was also carried out. Logistic analysis revealed that much of the variation in TSE practice was explained by a planning stage, implicating a two-stage motivation and volition stage rather than a five-stage model. In addition to explaining the characteristics associated with TSE practice and elucidating a stage approach to decision making, a draft health promotion programme was developed and evaluated. Two forms of the programme, a booklet and a seminar, were appraised and deemed effective as motivators of preventive action. Findings are discussed in terms of theory and practice of health education. The implications of the findings for health psychology are also discussed.