The charts of 84 patients admitted to the Neurosurgery Service of the Washington University Medical Center between January, 1960, and July, 1981, with aneurysms at or near the junction of the internal carotid and posterior communicating arteries (ICA-PoCA) were reviewed. Special emphasis was placed on the pupillary size and reactivity of 51 patients with oculomotor nerve involvement. Seven initially had normal pupils, representing 8% of the total group and 14% of those presenting with oculomotor palsies. In 4 of these patients pupillary involvement developed within 5 days, and in 1 pupillary involvement developed in 4 months. Pupillary sparing appears to be more common than previously appreciated in patients with ICA-PoCA aneurysms and oculomotor nerve involvement. Patients with acute somatic oculomotor paresis should be observed closely for at least one week for the development of pupillary involvement. Arteriography may be indicated more frequently than previously recommended.