Introduction: Genetic polymorphisms in codons 10 of the transforming growth factor β₁ (TGF-β₁) gene TGFB1 have been shown to be associated with the production of high or low TGF-β₁ levels. The role of this polymorphism in the development of prostate cancer and hyperplasia was investigated. Subjects and Methods: Using the allele-specific oligonucleotide polymerase chain reaction method, the association between the polymorphism at codon 10 of the TGFB1 gene and the risk of prostate cancer (PCa) or benign prostate hyperplasia (BPH) was determined. Results: Significant differences in the CC versus TT genotype distribution between PCa patients and male controls (p = 0.009), and between BPH patients and male controls (p = 0.005) were noted. Males with the TT genotype had a 1.67-fold increased risk of PCa and those with the TC/TT genotype had a 1.14-fold increased risk of PCa; males with the TT genotype had a 1.54-fold increased risk of BPH and those a with the TT/TC genotype had a 1.06-fold increased risk of BPH compared with those with the CC genotype. Conclusions: Based on our findings, it was possible to conclude that the codon 10 polymorphism in TGFB1 may have a significant influence on the development of PCa and BPH and that the T allele of the TGFB1 gene has a dominant effect on the development of PCa and BPH.