Modifications were introduced into the low ionic strength system of Lalezari. Glycine was added in place of acidified glucose and the sensitisation and aggregation phases were segregated. In the automated glycine system a stable baseline is readily obtained as strong cell aggregation, with risk of cell adhesion to coil walls, is restricted to the last few turns of the aggregation phase. The automated glycine system is sensitive to a concentration of 0.0015 microgram/ml of anti-D diluted in saline and to 0.006 microgram/ml of anti-D in serum. Antibodies of a broad range of specificity are detectable.