AIMS: To determine whether systemic hypertension and glaucoma might coexist more often than expected, with possible implications for treatment. METHODS: Case-control study using general practitioner database of patients with glaucoma matched with controls for age and sex. RESULTS: Hypertension was significantly more common in the 27,080 patients with glaucoma (odds ratio 1.29, 95% confidence intervals 1.23 to 1.36, p<0.001) than in controls. Treatment by oral beta blockade appeared to protect from risk (odds ratio 0.77, 95% CI 0.73 to 0.83, p<0.0001), but oral calcium channel antagonists or angiotensin converting enzyme (ACE) inhibitors did not (odds ratios 1.34, 1.24 to 1.44 and 1.16 1.09-1.24, respectively, p<0.0001 in each case). Oral corticosteroid treatment was associated with enhanced risk (odds ratio 1.78, 1.61 to 1.96). CONCLUSION: Common pathogenetic mechanisms in ciliary and renal tubular epithelia may explain coincidence of glaucoma and systemic hypertension. The choice of cardiovascular treatment, could substantially influence glaucoma incidence, with beta blockade protecting and ACE inhibitors or calcium channel blockers not affecting underlying risk.