A54145 is a complex of acidic lipopeptide antibiotics which are produced by Streptomyces fradiae and are active against Gram-positive bacteria. The A54145 complex was isolated by adsorption on Diaion HP-20 nonfunctionalized macroreticular resin and/or ion exchange on Amberlite IRA-68 anion exchange resin. Antibacterial factors A, A1, B, B1, C, D, E, and F were obtained in purified form by repeated preparative reverse phase HPLC on C8 and/or C18 bonded-phase supports. The molecular formulae of the factors are C72H109N17O27 (factors A and A1), C73H111N17O27 (factors B, B1, C, and D), C74H113N17O27 (factor E), and C71H107N17O27 (factor F). The identities of the acyl side chains were established as 8-methylnonanoyl (factors F, A, and B1), n-decanoyl (factors A1 and B), and 8-methyldecanoyl (factors C, D, and E).