In the course of our screening for novel antibacterial antibiotics produced by microorganisms, a strain termed KSM-2690 was found to produce a new complex of triene- β-lactone antibiotics in the culture filtrate. The active principle was recovered from the broth filtrate with ethyl acetate extraction and could be divided into six components, three major components KSM-2690 A (1), B (2) and C (3), and three minor components KSM-2690 D, E and F, on the basis of their respective order of elution under the reverse-phase HPLC. The characteristic UV and IR spectra of their components were similar to those of oxazolomycins1'2^ indicating that these new compounds are members of the triene-β-lactone group of antibiotics. Among them, the new antibiotics 2 and 3 presented here were an additional member of this group and its isomer, as shown in the gross structures. In this report, we describe preliminary taxonomic characteristics of the producing strain, fermentation, isolation, structural elucidation and biological activity of antibiotics 2 and 3.