The thermotolerant, ethanol-producing yeast strain, Kluyveromyces marxianus IMB3, was shown to produce ethanol at 45 degrees C on starch-containing media supplemented with a crude amylase preparation derived from the thermophilic, filamentous fungus Talaromyces emersonii CBS 813.70, Ethanol production on media containing 4% (w/v) starch increased to a maximum of 15 g/l with 40 h, and this represented 74% of the maximum theoretical yield. Subsequent experimentation involving growth of both organisms in fermentations on starch-containing media (4% w/v) demonstrated that the mixed-culture system was capable of ethanol production at 45 degrees C with maximum yields at 12 g/l obtained with 65 h. The advantages associated with ethanol production by this system are discussed.