Forty-three patients with glaucoma and 24 patients with ocular hypertension presenting with a retinal vein occlusion were medically assessed. The prevalence of systemic hypertension was 60.5% in those with glaucoma and 66.6% with ocular hypertension. The prevalence of hyperlipidaemia was 38.1% in those with glaucoma and 37.5% in those with ocular hypertension. These findings were compared with those from a carefully age-sex matched group of patients presenting with a retinal vein occlusion without evidence of glaucoma or ocular hypertension. There were no statistical differences between any of the groups (52.2% had systemic hypertension and 28.8% had hyperlipidaemia). There was also a strikingly high prevalence of systemic hypertension (89%) and hyperlipidaemia (55.5%) in nine of the patients who had evidence of a recurrent retinal vein occlusion associated with glaucoma, and these prevalence rates were strikingly similar to the rates in patients with recurrence but without glaucoma. The data suggest that glaucoma or ocular hypertension has a less prominent aetiological role in the development of a retinal vein occlusion than underlying medical causes and that full medical assessment is worthwhile.