Erwinia herbicols (strain A 111) produces two acylated peptide antibiotics herbicolins A and B. Isolation of herbicolins was performed by adsorption on a polystryrol adsorbent followed by elution with methanol. Further purification was achieved by gel filtration on Sephadex LH-20, counter-current distribution or by TLC. Herbicolin A was chemically characterized, containing 2 glycines, 1 L-threonine, 1 D-allo-threonine, 1 D-glutamic acid, 1 D-leucine, 1 L-agrinine and beta-hydroxy myristic acid. Herbicolins A and B are inactive against bacteria, but highly active against yeasts and filamentous fungi.