A perfusion system which utilizes a porous ceramic core has been tested for the cultivation of transformed BHK cells which produce human transferrin. A design is presented in which cells are immobilized within the porous ceramic particle and are fed by continuous perfusion of batch liquid medium. It was found that more than 5 x 10(9) BHK cells could be supported within the 40 mL ceramic matrix, a ten-fold increase in cell density per unit surface area over the standard roller bottle cultures or a five-fold increase in volumetric cell density over suspension cultures. The cell specific productivity of human transferrin was similar to that observed in suspension culture. The system offer the advantages of significant reduction in serum requirements and the potential for scale-up.