['Angiotensin I-converting enzyme (ACE), a type I cell surface zinc metallopeptidase, is differentially expressed in several malignancies and plays a role in tumor cell proliferation, tumor cell migration, angiogenesis, and metastatic behavior. We aimed to investigate the effects of ACE gene (rs1799752) variants on oral cancer risk.', 'Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) 32 was used to measure ACE gene polymorphisms in 88 patients with oral precancerous lesion (OPL), 186 33 patients with oral cancer, and 120 control subjects without any oral lesions. All study subjects were male 34 betel quid chewers.', 'Patients with oral cancer or OPL had a higher frequency of the DD genotype than the control patients did. Oral cancer patients with the DD genotype had a significantly higher prevalence of lymph node metastases than patients with the II/ID genotype did. After adjusting for age, smoking, drinking, and betel quid chewing status, we found that individuals with the DD genotype of the ACE gene had a 5.46-fold and 3.13-fold higher risk of developing oral cancer or OPL, respectively, than those with the II genotype did. Furthermore, oral cancer patients with the DD genotype of the ACE gene had a 2.16-fold higher likelihood of lymph node metastasis.'] Is polymorphism of angiotensin I-converting enzyme gene related to oral cancer and lymph node metastasis in male betel quid chewers?