Nature of proposed research A multi-stage study aimed at describing and explaining seasonal variation in sexual health risk, involving analysis of routine data on GUM clinic attendance, HIV testing; STI returns, births, termination of pregnancy; survey data on sexual beahviour and in depth and quantitative research with service attenders aimed at exploring the possible reasons for the variation, i.e. in terms of risk behaviour and risk reduction practice; health-seeking behaviour and availability of services. Prospective outcomes The expected outcome will be a body of rigorous and reliable data on seasonal patterns of sexual health. Expected benefits We will provide information which those working directly on the implementation of the Sexual Health Strategy may use to deliver more effective and better tailored and targeted sexual health promotion and service provision, and which those concerned with the training and professional development of health care professionals may use to ensure enhanced practice.