Objectives. The National Institutes of Health (NIH) organized the first International Prostatitis Collaborative Network workshop (November 5 and 6, 1998, Washington, DC) to address the confusion surrounding the diagnostic and treatment strategies in chronic prostatitis. Methods. A panel of North American and international urologic researchers, interested physicians, medical industry representatives, and patients were invited to participate and reviewed current definitions, classification systems, and recent epidemiologic and both published and "in progress" treatment studies. Results. A general concensus was developed for adoption of the following criteria for clinical studies in chronic prostatitis/chronic pelvic pain syndrome: (a) the NIH definition of chronic prostatitis/chronic pelvic pain syndrome; (b) the 1995 NIH Classification System; (c) the eligibility (inclusion/exclusion) criteria developed by the NIH Chronic Prostatitis Clinical Research Network; (d) the NIH Chronic Prostatitis Symptom Index. It was agreed that clinical treatment trials involving presently available, experimental, and theoretical therapeutic modalities be prioritized according to maximum potential benefits and that regulatory authorities (ie, Food and Drug Administration in the United States) consider major changes in the approval process for treatment modalities in chronic prostatitis. Conclusions. Chronic prostatitis is a major health care issue. Standardization of definitions, classification, study design, and outcome parameters will promote rational and comparative evaluation of diagnostic and therapeutic strategies. (C) 1999, Elsevier Science Inc.