BACKGROUND: To evaluate the significance of angioma number (single or multiple) for the presence of von Hippel-Lindau (VHL) disease in patients presenting with capillary retinal angioma. METHODS: Forty-one nonrelated patients presenting with capillary retinal angioma were evaluated. An ophthalmic workup, screening for other organ lesions, and molecular genetic screening for a mutation of the VHL gene was performed. The diagnosis of VHL was made on the basis of the personal and family history, the presence of other VHL-associated organ lesions, or the presence of a mutation of the VHL gene. RESULTS: Thirteen patients (32%) presented with a single angioma and 28 patients (68%) presented with multiple angiomas. In 81% of all patients, VHL could be diagnosed. Diagnosis of VHL could be readily made by the personal or family history in 51% of all patients. In another 27% of all patients, VHL disease was evidenced by screening for other VHL-associated lesions. In two patients (3%) VHL could be diagnosed by molecular genetics only. All patients with multiple retinal angiomas had VHL disease and, in 38% of patients with a single angioma, VHL was present. Reasons for a missing family history in patients with VHL disease were the presence of a de novo mutation (15% of VHL patients) or clinical anticipation of VHL disease (18% of VHL patients). CONCLUSION: The presence of multiple retinal angiomas strongly suggests VHL disease, which, however, can be obscured by presence of a de novo mutation or by clinical anticipation of VHL disease in affected families. A single retinal angioma may be sporadic as well as the presenting sign of VHL. Diagnosis and screening for this multitumor syndrome is substantially supported by molecular genetics.