This research objective is to test the efficacy of a new design of hollow fiber bioreactor for mammalian cell culture, and an integrated automated bioreactor control system. This research will investigate a hollow fiber bioreactor with optimized critical diffusional geometries combined with an integrated control system prototype which has Ph and dissolved oxygen (DO) monitoring and control capabilities. The bioreactor design uses concentric fibers to keep all cells immobilized within 200 microns of a diffusional oxygen source, and has supported hybridomas at high density (> 10/ml) and high viability ( > 85%) for 30 days. The system eliminates many failure modes of conventional hollow fiber reactors including bioreactor diffusional gradients, system autoclavability, peristaltic pump failure, and lack of Ph and DO controls. There are numerous diagnostic and therapeutic applications for developing in vitro cell culture methods and tissue models. There is a rapidly expanding market for cell culture equipment especially for the production of monoclonal antibodies (Mabs) and other secreted products. This market is actively pursuing alternatives to animals especially for therapeutic products. The goal of this research is to provide this market with a complete, compact, turnkey system for mammalian cell culture which is affordable ($12-15K), easy to use, and which solves many key failure modes of conventional reactor systems. This type of system could be used to produce 1-10 gram quantities of secreted products, cells for harvest or in vitro tissue analysis, and to optimize cell culture conditions.