In a retrospective study of 30 consecutive patients with symptomatic vasospasm the mean degree of narrowing as compared to the initial angiogram was 35% (+/- 24%) in 12 intradural internal carotid arteries (ICA), 42% (+/- 17%) in 42 proximal middle cerebral (MCA) and 38% (+/- 19%) in 27 anterior cerebral arteries (ACA). The corresponding increase in mean flow velocities from baseline values obtained by transcranial colour Doppler sonography (TCD) within 12 h of the first angiogram to the time of clinical vasospasm was considerably higher, with 49% (+/- 34%) in the ICA 119% (+/- 92%) in the MCA and 147% (+/- 170%) in the ACA. Following superselective intra-arterial papaverine application in 66 arteries and balloon angioplasty of 15 arteries, 78 (96.3%) of 81 dilated. Sustained clinical improvement was achieved in 22 patients (73.3%). The mean reversal of angiographic vasospasm was 71% for the ICA (range 10-100%), 81% for the MCA (range 9-100%) and 82% (range 0-100%) for the A1 segment. The mean reduction of flow velocities after treatment was much less with 23% (+/- 21%) in the ICA, 32% (+/- 24%) in the MCA and 25% (+/- 22%) in the A1 segment.