We used qualitative methods to explore factors, which might explain increased anxiety in patients attending a sexually transmitted infection (STI) clinic. Twenty patients, who scored significantly for anxiety on the Hospital Anxiety and Depression Scale (HADS) attended a 20-minute interview. This explored factors contributing to their current psychological symptoms. Transcripts revealed three main themes. First were factors related to possible STIs and the clinic visit. These included health anxieties about HIV or fertility and clinic factors, including staff attitudes and clinic location. Second were factors unrelated to the clinic, including previous emotional difficulties or substance misuse. Third were issues concerning stigma, embarrassment and shame. The origins of anxiety in STI patients are multifactorial and difficult to identify during brief appointments. Despite modern clinics and attitudes, stigma and embarrassment remain prominent. Interventions to address these factors could improve psychological health in this patient group.