Yeast cells producing the growth hormonesomatomedin C (SMC) were constructedand applied in the immobilized form continuouslyfor a period of over 10 days in a flowthroughbioreactor. The construction of theMF~I-SMC fusion vector p336/l is given as wellas the results of the influence of various nutrientseffecting hormone production. Immobilization ofthe transformed yeast cells is described and theirapplication in a continuous bioreactor system.This study demonstrates the feasibility of a longtermand high-level hormone production by immobilizedtransformed yeast. The SMC productivitiesof free cells in batch and immobilized cellsunder continuous conditions were 0.2--0.3 and0.5--0.6 mg per g wet cells and day, respectively.