A systematic approach to forecasting population prevalence on the island of Ireland in 2010 and 2015. Fore casts of population prevalence are useful to describe changing patterns of diabetes in the population and to support rational planning and development of services. In 2005 the Irish Diabetes Population Prevalence Working Group led by Ireland and Northern Ireland ’s Population Health Observatory (INIsPHO) at the Institute of Public Health in Ireland (IPH), produced estimates of population prevalence of diabetes for the island of Ireland. These estimates are based on the PBS model developed in the UK. In the second phase of this work forecasts of population prevalence of diabetes have been developed for 2010 and 2015.