Chlamydia is often asymptomatic and undetected may lead to painful and costly sequelae such as sub-fertility. It is therefore important to test young people at risk.The key aims of this project were to develop sustainable training in the delivery of basic sexual health services (particularly chlamydia testing) by GP staff to young adults, and to improve the detection rate of sexually transmitted infections. A Train the Trainer (TtT) package equipped professionals who train GP staff to then deliver CATTE (ChlamydiA Testing Training in Europe) to staff working within GP surgeries. CATTE aimed to develop the knowledge and skills GP staff require to provide Chlamydia testing and other sexual health services on a routine basis to young adult patients attending their practice.