We surveyed some novel nitrile hydratase-producing microorganisms through the enrichment culture technique at higher temperatures. We isolated several spore-forming filamentous bacteria from soil samples. One of them, strain 45A40 exhibited the highest nitrile hydratase activity. Based on taxonomical studies, strain 45A40 was identifind to be genus Streptomyces. It was the first example of a Streptomyces strain exhibiting high nitrile hydratase acitivity. We optimized the culture conditions of Streptomyces 45A40 to enhance the nitrile hydratase activity. The formation of nitrile hydratase was constitutive and was highly enhanced by the addition of cobalt ions. The enzyme acted on various nitriles and showed low Km value for 3-cyanopuridine. The enzyme exhibited tolerance against a high concentration of 3-cyanopyridine ; however, its heat stability was not outstanding.