In three Ínstructive čase reports the authors recall their experience with etiological diagnostics of the cau­sative lesion in Horneťs syndrome: The inborn form of the syndrome found in a 6-week old newborn followed up for 12 years. Anisocoria in Horneťs syndrome diagnosed on oneself by chance by a 60-year old physician fearing an intracerebral aneurysm. The picture was a part of cluster hemicrania and the čase report acquainting with its development over the next ten years. In a 50-year old hypertonie patient with amaurosis in one eye upon occlussion of arteria centralis retinae proceded by Horneťs syndrome following a lesion of periarterial n. sympathicus accompanying a sclerotic occlusion of the internal carotic artery. Followed up

        Key words: Horneťs syndrome - cluster hemicrania - occlusion of arteria carotis interna - heterochromia of the iris and inborn Horneťs syndrome.