OBJECTIVES Prostate cancer (PCa) incidence has been steadily increasing over the last twenty years, resulting in Ireland having the highest incidence rate in Europe in 2008.  The main driver of this is wide-spread use of prostate specific antigen (PSA) testing in primary care as an ad-hoc detection mechanism. The objective of this research was to undertake a cost-effectiveness analysis of organised screening using PSA testing in Ireland. METHODS Using a Bayesian Multi-Parameter Evidence Synthesis (MPES) framework, non-cost parameters were synthesised, informed by incidence, mortality and clinical data from the National Cancer Registry Ireland for men diagnosed with PCa in 2009.  The MPES framework estimates unobserved parameters using available evidence and so facilitates analysis of interventions where observational data is limited. Average costs were estimated using project-specific survey costs, Irish hospital costs (HSE Casemix) and costs published in the literature. Effectiveness of PSA testing was sourced from the literature. Utility scores were collected from 2,500 PCa survivors. The cost-effectiveness analysis employed a cohort, semi-Markov model following men from age 30 to death.  A range of PSA screening strategies were compared with no PSA testing and an extensive series of scenario analysis was employed. PSA cut-off levels were varied between >3ng/ml and >4ng/ml reflecting European guidance and practice variation in Ireland. Costs and benefits were discounted at 5% per annum.   RESULTS Extensive probabilistic sensitivity analyses highlighted wide variation in incremental cost-effectiveness ratios (ICERs). PSA testing may be cost effective using a once-off test at age 50 or age 55 depending on the ceiling ratio incorporated. Results for the ≥3ng/ml PSA cut-off consistently dominated those for the ≥4ng/ml PSA cut-off.   CONCLUSIONS This analysis illustrates the value MPES methods for economic modelling of interventions. The results contribute to the ongoing accumulation of evidence on the costs and benefits of PSA testing internationally.