Objectives. This study aimed to improve understanding of how young UK genito-urinary medicine (GUM) patients perceive the risk of chlamydia, and identify implications for health education. Design. A qualitative methodology was chosen. Methods. Semi-structured interviews with 27 respondents aged 16-22 years old were conducted. Data were subjected to thematic analysis. Results. Respondents made assessments of the perceived seriousness of, and their personal susceptibility to, chlamydia infection. Judgements about seriousness were related to beliefs about the controllability of symptoms and the long-term health consequences of infection. Susceptibility estimates were related to beliefs about the extent to which personal exposure put them in contact with chlamydia, and about the prevalence of infection amongst their peer group. This is consistent with the content of illness risk representations proposed by Cameron (2003). Respondents demonstrated some beliefs, which appeared to influence perceptions of seriousness and susceptibility in unhelpful ways. Conclusions. Young people may be underestimating their risk of chlamydia infection due to the presence of unhelpful beliefs. Dialogue between health professionals and patients within GUM clinics, or through consultations as part of the National Chlamydia Screening Programme (NCSP), could provide vehicles to deliver health education to target these. Suggested health education includes highlighting false reassurance provided by treatment beliefs and exposing the fallibility of using overt characteristics to judge the likelihood that a potential sexual partner poses a risk of infection. ©2011 The British Psychological Society.