a contained, crossflow filtration (cff) membrane system is described for harvesting saccharomyces cerevisiae and escherichia coli cells. this system is portable and can be cleaned and sanitized in place. low-and high-cell density (lcd, hcd) fermentations of recombinant cells in 10- to 200-l volumes were used as the starting material. lcd fermentations, up to 8.3 g l** $minus$ **1 dry weight (dcw) of s. cerevisiae, with volumes of 10 to 200 l were harvested and diafiltered in 0.5 and 1.5 h, respectively. hcd 200-l fermentations of s. cerevisiae (47-63 g l** $minus$ **1 dcw) were harvested and diafiltered in approximately 2 h. e. coli fermentations, lcd and hcd (up to 16.2 g l** $minus$ **1 dcw), of 200-l volumes were harvested and diafiltered in 2.3 h while employing 14 and 75 ft**2 of membrane area, respectively. using hollow fiber or flat sheet membranes from different sources, cell harvesting times were less than 2.5 h. these studies demonstrate that cff is an efficient method for harvesting and diafiltering recombinant s cerevisiae and e. coli cells from fermentation broth. (author abstract) 17 refs