The last decade has seen a resurgence of interest and exciting new research on chronic prostatitis and related syndromes. One important reason for this enthusiasm is the recognition that chronic prostatitis syndromes represent an important worldwide health care problem. New data suggesting that chronic prostatitis syndromes may have important long-term consequences are a second reason for the resurgence of research interest. This article reviews the new classification of chronic prostatitis syndromes. Emphasis is then given to summarizing new data on the epidemiology of chronic prostatitis. We concentrated on population-based studies employing reasonable case-definitions to survey various populations from North America, Europe and Asia. These studies suggest that prostatitis syndromes are common, with 2-10% of adult men suffering from symptoms compatible with chronic prostatitis at any time. Approximately 15% of men suffer from symptoms of prostatitis at some point in their lives. Preliminary epidemiological and biological studies also suggest that chronic prostatitis may be associated with an increased risk for development of benign prostatic hyperplasia and prostate cancer. These findings support the conclusions that chronic prostatitis is an important international health care problem that merits increased priority from clinicians as well as increased clinical and basic science research.