A comparative study on the cultivation of Digitalis lanata suspension cells in polyurethane foam matrix and Ca-alginate gel was performed to investigate the effects of immobilization on the production of digoxin from digitoxin by biotransformation. While polyurethane foam immobilization did not affect cell viability, the growth of Ca-alginate entrapped cells was considerably inhibited. When 200mg/ℓ of digitoxin was added, maximum digoxin production of 51.12mg/ℓ was achieved at the first day of biotransformation in free cell suspensions. On the other hand, maximum digoxin production was 52.37mg/ℓ in polyurethane foam entrapped cell cultures after 2 days of biotransformation. This result suggests that the utilization of potential advantages of immobilization technique is feasible. Maximum digoxin production in Ca-alginate entrapped cells was, however, only 25.43mg/ℓ after 2 days of biotransformation. The reason for this low yield was probably due to the low cell growth and viability caused by Ca-alginate immobilization. It was also found that the cells immobilized in polyurethane foam matrix produced much less digoxin compared to free cell suspensions with addition of 400mg/ℓ of digitoxin, even though the digoxin productivities of both cultures were almost the same in the case when digitoxin addition was below 200mg/ℓ. It can be thus concluded chat the addition of high concentration of substrate should be prevented for immobilized cells.