Plasma big endothelin (BE) levels were studied in 17 patients during the first 2 weeks following spontaneous intracerebral hemorrhage (ICH). Three patients had experienced an infratentorial hemorrhage of the pons and cerebellum. The group of 14 patients with supratentorial hemorrhage presented with 8 hematomas of the putamen, 4 of the capsula interna and 2 in the thalamus. Significant elevations of BE during the first 2 weeks after the initial ICH, significant differences between the different localisations and between patients with different prognoses were not apparent (mean BE level: 2.95 ± 1.39, control group: 2.68 ± 1.29 fmol/ml). These results support the theory that endothelins do not play a significant pathophysiological role in acute severe IC