Benign changes ranging from atrophy and inflammation to high-grade prostatic intraepithelial neoplasia (HGPIN) are common findings on prostate core needle biopsies. Although atrophy and inflammation may be precursors of prostate cancer, only HGPIN is currently recommended to be included in surgical pathology reports. To determine whether these benign findings increase prostate cancer risk, we conducted a case-control study nested within a historical cohort of 6692 men with a benign prostate specimen collected between 1990 and 2002. The analytic sample included 574 case-control pairs comprised of cases diagnosed with prostate cancer a minimum of 1 year after cohort entry and controls matched to cases on date and age at cohort entry, race, and type of specimen. The initial benign specimen was reviewed for presence of HGPIN, atrophy (simple, lobular, and partial) and inflammation (glandular and/or stromal). HGPIN significantly increased risk for prostate cancer (odds ratio (OR)=2.00; 95% confidence interval (CI)=1.25-3.20). Inflammation within the stromal compartment was associated with decreased risk (OR=0.66; CI=0.52-0.84), and diffuse stromal inflammation of severe grade had the strongest inverse association with risk (OR=0.21; CI=0.07-0.62). In a model adjusted for prostate-specific antigen (PSA) level at cohort entry and inflammation, simple atrophy was associated with a 33% increased prostate cancer risk that was marginally significant (P=0.03). Clinicians should consider patterns and extent of inflammation when managing high-risk patients with negative biopsy results. Identifying benign inflammatory processes that underlie high PSA levels would help to reduce the number of unnecessary repeated prostate biopsies.