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Verticillium chlamydosporium produced in submers culture several antifungal and/or phytotoxic compounds which were detected in a bioassay by using the pathogen‐host system Puccinia coronata and oat seedlings. The antifungal compounds were also tested against P. recondita on wheat and P. sorghi on corn seedlings. The production of the active metabolic compounds highly depended on the nutrient solution (peptone‐Czapek [PC] and malt extract [ME]) and on the fermentation times. Cell‐free filtrates of PC‐cultures of the fungus were highly phytotoxic; the fungitoxic and phytotoxic compounds were heat‐labile and dialyzable. The ethyl acetate extracts of the PC‐culture filtrates contained only the antifungal active substances. The antifungal compounds in ME‐culture filtrates proved to be heat‐stable, could be dialyzed and extracted with ethyl acetate. Ethyl acetate extracts of PC‐ and ME‐culture filtrates at concentrations of 500 μg/ml reduced rust disease incidence by up to 80 % compared to the control treatment. Further studies with extracts of ME‐culture filtrates displayed a distinct protective but no systemic activity. The extract interfered with the development of several infection structures of the rust fungi, mostly with the growth of germ tubes as well as with the formation of the aappressoria and haustorial mother cells. Three rust‐active fractions were obtained by preparative layer chromatography on silica gel. One of these fractions exhibited phytotoxic activity. The most active antifungal fraction is identical with the macrolid antibiotic monorden which caused a desorientated spiral growth in P. coronata germlings on oat leaves.