A series of new lipopeptides, circulocins a±d (1±4), was isolated from the fermentation broth of Bacillus circulans, J2154. These compounds exhibited potent antibiotic activity against the Gram-positive bacteria, including the piperacillin-resistant Streptococci and vancomycin-resistant Enterococci. Their structures were established using spectroscopic methods, and the absolute configurations were determined by amino acid analyses. q 2001 Elsevier Science Ltd. All rights reserved.