An automated readout device recording light transmission in the eight channels of the BG-8, blood-grouping machine after removal of agglutinates is described. Using a continuous recording of positive or negative signals in the eight channels independently, 7.5% of 10,000 blood group determinations had to be retested because of clots in the samples, lacking reactions or excess reactions on the recorder. No incorrect recordings of blood groups were obtained, however. Using anti-D serum together with anti-CDE serum, the rhesus D factor was correctly detected in 99.92% of 3,891 samples, and the Du factor was detected in all 5 samples known to carry this antigen. Using a discontinuous recording of integrated and synchronised signals, adapted to fully automated data processing, another 5% of the samples had to be retested because of inadequate phasing of the reactions in the eight channels of the BQ-8. The results described are influenced by the poor quality of the blood samples used for the study.