In the course of our screening for new antibiotics, a Streptomyces strain YN-0165J isolated from a soil sample collected at Omaezaki in Shizuoka Prefecture, Japan, was found to produce a new antibiotic. The strain YN-0165J is classified in the genus Streptomyces on the basis of morphological and chemical characteristics. The antibiotic YN-0165J-A was isolated and purified, and its physico-chemical properties were determined. It is classified in the enteromycin group but differs from known antibiotics in this group. Analytical and spectroscopic data suggested its structure as 4-[2-(N-oxidemethoxyimino)acetamide]butylamide, leading to the conclusion that YN-0165J-A is a new antibiotic. Its antimicrobial activity was also tested.