An antifungal protein of about 30,000 Da was isolated from seeds of Sorghum bicolor L. using chromatographic techniques, including gel filtration, ion exchange, and high-performance liquid chromatography in a reverse-phase column. This protein (termed 30 kD protein) showed a minimal inhibitory concentration of 36 microg/ml for Candida parapsilosis and C. tropicalis, and 18 microg/ml for C. albicans. The 30 kD protein inhibited adherence to the cover glass and formation of a germinative tube of C. albicans at concentrations over 300 and 150 microg/ml, respectively. Transmission electron microscopy of yeast forms of C. albicans after incubation with 18 mug/ml of the 30 kD protein for 24 h revealed marked ultrastructural changes in the fungus. No toxicity of the 30 kD protein to the culture of Hep2 cells at concentrations equal to or less than 1,000 microg/ml was observed.