Cells of Cephalosporium acremonium ATCC 48272 immobilized in calcium alginate beads were utilized for cephalosporin C production and the results were compared with those obtained with free cells. The experiments were performed with synthetic medium containing glucose and sucrose as carbon and energy sources. Experimental effectiveness factor values were obtained at various cell and dissolved-oxygen concentrations, considering Monod kinetics for the respiration rate, and were compared with the values calculated with zero-order kinetics in spherical bioparticle. The results showed that the assumption of oxygen limitation by diffusion in the bioparticle was correct, and that cephalosporin C production with immobilized cells is perfectly viable, although a slightly lower rate than that obtained in the free cell process was observed.