[Cryopreservation of erythrocytes: detailed quality control]

It has been well established that cryopreservation of red cells with glycerol is a suitable method for long-time storage. Therefore, many data for quality control have been published. Most measurements, however, are restricted to the final product. Less information is available about the particular steps of cryopreservation. The present paper describes in detail the results of quality control measurements during the procedure. Although the final product meets the demand of the WHO for cryopreserved red cells, it could be demonstrated that erythrocytes are remarkably damaged by the deep-freezing process. Further experiments seem to be necessary in order to improve the details of the deep-freezing procedure.