The beta-galactosidase specific activity values obtained with the high-throughput procedure are identical to those obtained by the traditional single-tube method of Miller. Thus, values obtained with this procedure may be expressed as Miller units and compared directly to Miller units reported in the literature. The 96-well format for permeabilization and assay of enzyme specific activity together with the use of 12-channel and repeater pipettors enables efficient processing of hundreds of samples in an 8-h day.