growth of a hybridoma culture, along with production of monoclonal antibody, was demonstrated over extended periods in polysulfone hollow fiber membrane modules. the molecular weight cutoffs of the membranes were 10,000, 50,000, and 100,000 daltons the hybridoma cell line, designated 65/26, produced igg (2b/ $kappa$ ) directed at mouse thymus cell surface antigen, tl. 1. cell growth occurred in the shell space of the reactor, using supplemented rpmi 1640 (20 fetal bovine serum) supplied from a separate reservoir vessel through the hollow fiber lumen. the reservoir contained 125 ml media, which was changed every 4 days. concentrations of immunoglobulin were determined by an enzyme immunoassay (using protein a and alkaline phosphatase-labeled antibody conjugate). for the 10k, 50k, and 100k hollow fiber membrane modules, the maximum igg concentrations detected in the 2. 5-ml shell space were 47. 5-80, 510, and 740 $mu$ g/ml, respectively. (edited author abstract) 32 refs