Heat generation due to eddy currents and hysteresis induced by alternating magnetic field was utilized for the enhancement of ethanol formation catalyzed by immobilized yeast. A gel containing 2% sodium alginate, 4.2% dry yeast and 15, 30 or 50% iron powder (or Ba-ferrite) was prepared in CaCl2 solution to immobilize the yeast. The gel was cut into cylindrical pieces of phi2 mm x 2 mm. The cylindrical pieces of gel were placed inside a column through which culture medium flowed at a constant temperature. The ethanol concentration increased by 12% with immobilized yeast containing 50% iron powder at 5,000 Hz and 200 Oe of alternating magnetic field due to eddy currents. A similar result was obtained (14% increase) using immobilized yeast containing 50% Ba-ferrite at 2,000 Hz and 400 Oe of alternating magnetic field due to hysteresis. These effects corresponded to a 4-degrees-C rise in temperature in the gel.