Four patients with symptoms and signs of brain stem ischemia due to occlusive disease of the vertebrobasilar system and one patient with similar cerebrovascular disease who was thought to be prone to brain stem stroke underwent a microvascular anastomosis between the occipital artery and the caudal loop of the posterior inferior cerebellar artery. There was no morbidity of mortality and neurologically all patients improved. Post-operative angiograms showed patent anastomosis in all the patients and improved circulation in three. This new operation may prove beneficial in a selected group of stroke patients who suffer from vertebrobasilar insufficiency and cannot be treated with gross surgical techniques.