Two new 7-formamidocephalosporins have been isolated as their acetyl derivatives (SQ 28,516 and SQ 28,517) from fermentations of a Flavobacterium sp. SC 12,154. Structure 1 was deduced for SQ 28,516 from its spectroscopic properties while structure 2 was proposed for SQ 28,517. SQ 28,516 exhibits weak antibacterial activity.