Panomycocin, the killer toxin of Pichia anomala NCYC 434 (K5), is a 49 kDa monomeric glycoprotein with exo-beta-1,3-glucanase activity (patent pending). In this study we evaluated the in vitro activity of panomycocin against a panel of 109 human isolates of seven different pathogenic Candida spp. using microdilution and time-kill methods. Panomycocin was most active against C. tropicalis, C. pseudotropicalis and C. glabrata with MIC90 values of 1 mu g/ml. It displayed significant activity against C. albicans and C. parapsilosis with MIC90 values of 4 and 2 mu g/ml, respectively. For C. krusei, the MIC90 value was 8 mu g/ml. Panomycocin was fungicidal against all the tested Candida spp. The MFC values were only one or 2 dilutions higher than the MICs with the exception of C. krusei isolates with MFCs greater than or equal to 4 X MIC. Results of this study indicated that panomycocin could be considered as a natural antifungal agent against Candida infections and has significant potential for further investigation.