When screening for inhibitors of endothelin-converting enzyme (ECE), we isolated and identified Aspergillomarasmine A and B (AM-A and B) as potent inhibitors of ECE from the culture broth of Paecilomyces sp. N877. Both AM-A and AM-B had apparent activity in an in vivo experiment with big ET -1 induced sudden death, although the inhibitory activities of these compounds would be mainly due to the chelating effect.