The Glutathione S-transferase M1 (GSTM1) gene is reported to be involved in glaucoma, an eye disease with a largely unknown mechanism. The gene is polymorphic and three alleles have been characterized. These are one complete deletion of the gene, GSTM1*0, and two alleles differing only in a single amino acid substitution, GSTM1*A and *B. The two latter alleles seem to have equivalent function. Approximately 45% of the European populations are GSTM1 positive. An Estonian study has found that 60% of the glaucoma patients are GSTM1 positive as compared to 45% of controls (P=0.002). We genotyped 200 primary open angle glaucoma patients (POAG), 188 exfoliative glaucoma patients and 200 matched controls using multiplex PCR and pyrosequencing. Forty four per cent of the POAG patients and exfoliative glaucoma patients, and 44.5% of the matched controls were GSTM1 positive. Using pyrosequencing we were able to determine if the patients were homo- or hemizygous for the GSTM1 gene. Five per cent of the POAG patients, 7.4% of the exfoliative glaucoma patients and 4.6% of the controls were homozygous for the presence of the GSTM1 gene. There is no evidence of association between GSTM1 and glaucoma in the Swedish population.