The myocilin (MYOC) gene promoter polymorphism -1000C>G (MYOC mt.1) can be associated with faster progression of primary open angle glaucoma (POAG). The purpose of this study was to investigate the MYOC mt.1 in Brazilian patients with POAG and to evaluate its possible role on the phenotype and the severity of the disease.One hundred sixty-seven POAG patients and 130 normal controls were enrolled. DNA samples were prepared and the MYOC mt.1 polymorphism was screened by real-time polymerase chain reaction (RT-PCR) in an Single-nucleotide polymorphism (SNP) assay. Frequencies of the MYOC mt.1 promoter polymorphism were determined for both groups and compared by Fisher's exact test and Chi-square test with Yate's correction. Intraocular pressure (IOP), cup-to-disc ratio (C/D), number of glaucoma medications, and number of glaucoma surgeries were compared between MYOC mt.1 carriers and non-carriers.MYOC mt.1 genotype frequencies did not differ between POAG and controls (P = 0.420); 14.6% of controls and 16.4% of POAG patients were MYOC mt.1 carriers (CG or GG). Frequencies of the G allele were similar between glaucomatous patients and controls (7.3% and 9.2%, respectively; P = 0.477). Among POAG patients, there were no differences in mean C/D ratio, IOP, number of glaucoma medications, and surgical procedures for IOP control between carries and non-carriers of the MYOC mt.1 promoter polymorphism (p>0.05).The G allele of the MYOC mt.1 promoter polymorphism was equally distributed among POAG patients and healthy subjects and it is possibly unrelated to the risk and severity of disease in the Brazilian population.