A novel antibiotic, lactivicin (LTV), was isolated fran the culture filtrates of two bacterial strains by various types of chrcmatcgrapby. LTV exists in aqueous solution as an eguilibrium mixture of two epiamsrs in a ratio of about 1:l. The chemical structure of LTV (~OH,~N~~) was determined to be 2- (4S-acetylamirrz-3-oxo-2-isoxazolidinyl)-5-oxo-tetrahydrofuran-2-carbcqlic acid. The absolute configuration at the C-6 position was elucidated from the CD spectral data and X-ray crystallcgra@ic analysis of rl-amino-lactivinic aid obtained by the iminoether method. This canpound is useful as a starting material for chemical tification. LTV showed antibacterial activity against Gram-positive and negative bacteria, susceptibility to B-lactanmxs, armd affinity for penicillin-binding proteins. We therefore concluded that LTV is a novel skeleton antibiotic having &lactxm-like activities.