The yield of fibrinolytic and other proteolytic enzymes by Ca-alginate immobilized cells of Penicillium chrysogenum H9 was compared to that of free cells. The gel matrix protected the immobilized cells from lysis providing higher stability to the biocatalyst. The highest fibrinolytic activity/caseinase activity ratio was obtained in immobilized cell cultures. The composition of culture medium influenced enzyme production, showing different patterns in free and immobilized cultures. An alginate concentration of 3% and 10 ml alginate beads/50 ml medium were optimum for fibrinolytic enzyme biosynthesis. Semicontinuous production of the enzyme indicated the superiority of immobilized cells. The beads were affected by repeated exposure to phosphate ions after 12 cycles.