New alkaloid antibiotics named kobutimycins A (1) and B (2) (Fig. 1) were isolated from the culture broth of a streptomycete strain No. TA3341, which was isolated from a soil sample collected at Kobutizawa, Yamanashi Prefecture, Japan. The strain has been classified as Streptomyces sp. TA3341. In this communication we wish to report the fermentation, isolation, structural elucidation and biological properties of kobutimycins.