Primary open angle glaucoma (POAG) is the second most common cause of blindness in developed countries. It is an optic neuropathy in which a degeneration of the retinal ganglion cells causes a characteristic excavation in the optic disc. Several loci have been identified to be responsible for different types of glaucoma, including the MYOC gene located on chromosome 1. In this work, six mutations have been identified in the third exon of the MYOC gene in patients with POAG. We studied 79 Galician patients with chronic POAG glaucoma and 90 control individuals from the same general population. We identified six mutations, including three novel ones. Two of the six mutations were considered to be polymorphisms, while the other four met the criteria for pathogenicity in this disease as they altered the amino acid sequence and were found in one or more patients with glaucoma and in less of 1% of the control population. These mutations were detected in eight patients suffering from POAG (7.5%) and in two people from the control population (2.2%). POAG can be due to mutations in the myocilin gene (MYOC) on chromosome 1. The glaucoma phenotype associated with this gene may vary from a juvenile severe form to a late-onset chronic open angle glaucoma.