In two groups of 11 patients with poor prognosis malignancies undergoing high-dose sequential chemotherapy, we have evaluated the cryopreservation of blood cell transplants with oxypolygelatine-containing (55% oxypolygelatine, 6% hydroxyethylstarch, 5% dimethyl sulfoxide) vs standard human serum-containing (55% human serum, 6% hydroxyethylstarch, 5% dimethyl sulfoxide) cryoprotectant mixtures. Evidence is presented demonstrating that substitution of human serum proteins with oxypolygelatine has no detrimental effect either in vitro on the post-thawing recovery of hematopoietic progenitors or in vivo on the capacity of marrow reconstituting function in patients treated with myeloablative cancer therapy and autologous blood cell transplant. Oxypolygelatine is commercially available for clinical use as a plasma expander, is 30-fold less expensive than human serum albumin, is certified free of foreign serum proteins and antibodies as well as free of pyrogen, viral, mycoplasmal and bovine spongiform encephalopathy contaminants. Because of these characteristics, oxypolygelatine permits avoidance of: (1) the use of expensive serum albumin; (2) the fastidious preparation of autologous plasma or serum, and (3) the risk of infection associated with the infusion of allogeneic serum. Because of these practical advantages, we recommend the clinical use of oxypolygelatine as a substitute for human serum proteins for the routine cryopreservation of blood cell transplants.