A process of producing a receptor in HEK-293 cells used for the drug discovery program at Pfizer Inc. has been successfully developed with a novel BelloCell bioreactor to replace the conventional 2-D cell culturing devices including Cell Factories and roller bottles. A single BelloCell-500 has produced >1.4 x 10(9) HEK-293 cells, which are equivalent to those produced by 12 roller bottles, with substantially easier operation, single inoculation, less inoculum, less medium consumption and better space utilization. The receptor expression levels are better than those obtained by the traditional process. 3.7 pmoles of radioligandY mg(-1) protein were attained in the bioreactor compared to 2.3 pmoles of radioligandY mg(-1) protein in roller bottles. This may be attributed to the three dimensional attachment during cell growth. A 92% cell recovery from the bioreactor has been attained using Acutase or Trypsin treatment followed by four washes. It has been proven to be a viable and efficient device to produce adherent cells and express target components of interest for drug discovery applications.