The structure of a new antibiotic, roseophilin, was elucidated to be as shown iu Fig. 1 by NMR spectral analysis including a variety of two-dimensional techniques. Roseophilin was found to possess a novel skeleton containing pyrrole and furan moieties. In the course of our screening for new antitumor antibiotics, a novel active substance, roseophilin (1). was isolated from the culture broth of an actinomycete identified as Streptomyces griseoviridis. The compound showed cytotoxicity against KS62 human erythroid leukemia cells (Q, 0.34 PM) and KB human epidermoid carcinoma cells (It&, 0.88 l&I). We report here the isolation and structural elucidation of 1 (Fig. 1).