The effects of the Penicillium. chrysogenum low molecular mass antifungal protein (PAF) on selected fungal species belonging in the Zygomycetes were investigated. A total of 21 fungal isolates from 15 different genera (Absidia, Actinomucor, Cokeromyces, Gilbertella, Micromucor, Mortierella, Mucor, Mycotypha, Rhizomucor, Rhizopus, Saksenaea, Syncephalastrum, Thamnostylum, Umbelopsis and Zygorhynchus) were tested. The inhibitory potentials of PAF at 50 microg ml(-1) on the germination of the sporangiospores and at 6.25-50 microg ml(-1) on the hyphal extension were examined on different culture media. From among the fungi regarded as opportunistic human and/or animal pathogens, PAF exhibited inhibitory effects against Absidia, Mortierella, Rhizomucor and Rhizopus species.