Cephalosporins generated antifungal principle(s) during their degradation in aqueous solution though their antibacterial property is lost progressively during this process. The degradation product(s) from cephalexin, cefadroxil, cephacetril and cefazolin showed high activity against the dermatophytes of the genus Trichophyton, Microsporum, and Epidermophyton. Growth of a plant pathogen Macrophomina phaseolina was also weakly inhibited. Unlike the cephalosporins none of the penicillins tested produced such an antifungally active substance in aqueous solution. The nature of antimycotic activity generated from cefazolin was different from that produced from cephalexin, cefadroxil and cephacetril. Copyright © 1992, Wiley Blackwell. All rights reserved