CGS 26303, a dual inhibitor of endothelin-converting enzyme-1 (ECE-1) and neutral endopeptidase 24.11, was previously shown to prevent and reverse vasospasm in an experimental model of subarachnoid hemorrhage (SAH). However, reversal of the vasospastic response was not very efficacious. This study was designed to examine the effects of a highly selective ECE-1 inhibitor, CGS 35066, on SAH-induced cerbrovasospasm. Experimental SAH was induced in New Zealand white rabbits by injecting autogenous blood into cisterna magna and CGS 35066 was injected i.v. twice daily, either at 1 h (prevention protocol) or 24 h (reversal protocol) after SAH. Treatment with CGS 35066 significantly attenuated basilar arterial narrowing at a dose of 1 mg/kg in both protocols. These findings provide support for the use of selective ECE-1 inhibitors for the treatment of SAH-induced vasospasm even after the process of arterial narrowing has begun.