A novel anti-inflammatory compound, Sch 36605, belonging to the blasticidin family of nucleoside compounds was isolated from the fermentation filtrate of a Streptomyces sp. Sch 36605, as well as blasticidin S, demonstrated anti-inflammatory activity in the reverse passive Arthus reaction and the adjuvant arthritic rat at doses ranging between 1 ~ 10 mg/kg and 0.3 ~ 6.0 mg/kg, respectively. A minor component, Sch 36606, co-produced in the fermentation was isolated and identified as a known compound in the blasticidin family of compounds. In our screening program for unique microbial products with pharmacological activity, a fermentation filtrate from a Streptomyces sp. showed anti-inflammatory activity. The major active component, Sch 36605, was purified and identified as a novel nucleoside related to blasticidin S1,2). In addition, a closely related minor component, Sch 36606, was also isolated and identified. This paper describes the taxonomy and fermentation of the producing culture, and the isolation and biological properties of the active components. Details of the physico-chemical properties and structure elucidation are reported in a separate paper3).