In the course of our screening program for free radical scavenging substances from microorganisms (expected to be useful as therapeutic reagents for myocardial and cerebral ischemia, atherosclerosis, and inflammation), we isolated novel substances named neocarazostatins A, B and C from the culture of Streptomyces sp. strain GP38. Their physico-chemical properties were determined (Table 1). Since the UV absorption spectra of neocarazostatins are very similar to that of carazostatin and those of carbazomycins, the existence of a carbazole nucleus was suggested in each compound. Structural elucidation using 1H, 13C NMR, HMBC, and COSY spectra revealed the structure of neocarazostatin A, and neocarazostatins B and C were also characterized. These substances are novel free radical scavengers.