This Evidence Check review reports on the effectiveness of interventions which aim to reduce the transmission of three Sexually Transmissible Infections (STIs): chlamydia, gonorrhoea and syphilis. Interventions of interest included testing, treatment, partner notification and prevention of re-infection. These interventions are examined in five settings: primary health care, sexual health services, Aboriginal Community Controlled Health Services, antenatal services and services for young people. Substantial evidence for the effectiveness of a broad range of interventions is identified. There are wide variations in the level of resources which are required, with the more expensive interventions not always shown to be the most effective.