Clinicians should recognise that older patients are often sexually active and, therefore, at risk of sexually transmitted infections. Syphilis and HIV are two such infections with particular relevance in an older population, since the morbitity of other infections mainly affects fertility, which is of little worry in older patients. Since 1998, diagnoses of syphilis have been increasing in the UK, and late effects of earlier epidemics may be seen as untreated, latent, or symptomatic syphilis. In the case of HIV, effective antiviral treatment has increased the lifespan of patients and an increasing number of new diagnoses are made in older patients.