A number of penicillium strains belonging to the species Penicillium roqueforti, P. crustosum, P. paneum Frisvad, and P. chrysogenum were analyzed for their ability to produce the mycotoxins isofumigaclavine A, isofumigaclavine B, festuclavine, roquefortine C, and PR toxin when cultured on three different media. Some of the strongest mycotoxin-producing strains were later inoculated into samples of must (grape juice) before and after wine fermentation. After incubation at 25 degrees C for 1 and 2 weeks it was found that all except one of the penicillium strains were able to produce one or more of the toxins analyzed. However, the types of toxins as well as toxin concentrations varied a great deal, depending on culturing medium or culturing time. The media containing yeast extract normally gave higher toxin levels. From the wine experiments it was shown that isofumigaclavine A can be formed under certain circumstances in must and wine. A qualitative High Performance Liquid Chromatography (HPLC) method for simultaneous determination of isofumigaclavines A and B, roquefortine C, and PR toxin was also developed.