OBJECTIVE—The aim of this study was to examine associations between diabetes and clinical markers of benign prostatic hyperplasia (BPH) in community-dwelling white and black men aged 40–79 years. RESEARCH DESIGN AND METHODS—Data from the Olmsted County Study of Urinary Symptoms and Health Status and the Flint Men's Health Study were combined for a total study sample of 2,484 men. Severity of lower urinary tract symptoms (LUTS), peak urinary flow rates, prostate volume, and serum prostate-specific antigen (PSA) levels were examined by self-reported physician-diagnosed diabetes. RESULTS—Overall, 170 men (6.8%) reported a history of diabetes. Increased irritative LUTS and specifically nocturia were positively associated with diabetes. These patterns were consistent across race and persisted after adjustment for age, BMI, and various indicators of socioeconomic status. Furthermore, the relationship between irritative LUTS and diabetes was greater in black men. No significant associations were observed between diabetes and prostate volume, PSA level, and peak urinary flow rate. CONCLUSIONS—Our multiethnic community-based study demonstrates positive associations between diabetes and irritative LUTS and nocturia. Moreover, the association between irritative LUTS and diabetes is increased in black men. There was no strong evidence for an association between diabetes and BPH across measures more specific to BPH (i.e., prostate volume, PSA, and peak urinary flow rate). Taken together, our findings suggest that the presence of diabetes may be less related to prostate growth and more related to the dynamic components of lower urinary tract function. Further evaluations of the association between diabetes and BPH and related racial variations are warranted.