Background: The association between benign prostatic hyperplasia (BPH) and prostate cancer (PCa) remains controversial, largely due to a detection bias in traditional observational studies. Objective: To assess the association between BPH and PCa using inherited single nucleotide polymorphisms (SNPs). Design, setting, and participants: The participants were White men from the population-based UK Biobank (UKB). Outcome measurements and statistical analysis: The association between BPH and PCa was tested for (1) phenotypic correlation using chi-square, (2) genetic correlation (rg) based on genome-wide SNPs using linkage disequilibrium score regression, and (3) cross-disease genetic associations based on known risk-associated SNPs (15 for BPH and 239 for PCa), individually and cumulatively using genetic risk score (GRS). Results and limitations: Among 214 717 White men in the UKB, 24 623 (11%) and 14 311 (6.7%) had a diagnosis of BPH and PCa, respectively. Diagnoses of these two diseases were significantly correlated (χ2 = 1862.80, p