'Cryohydrocytosis' is an unusual human haemolytic anaemia of the 'hereditary stomatocytosis' group, in which the red cell membrane is abnormally permeable to Na and K+ at both body and (even more prominently) refrigerator temperatures. If whole cryohydrocytosis blood is anticoagulated in heparin or EDTA and stored on ice overnight, about 50% of the cells will lyse. Citrate phosphate dextrose adenine (CPDa) anticoagulant, empirically verified as an optimal anticoagulant for storage of normal blood before transfusion, very markedly ameliorated this overnight lysis, suggesting that these cells might form an informative model in which cold storage of the red cell could be studied in a short time scale. Accordingly, we conducted studies of ion flux, cell swelling and lysis in different media used historically for blood preservation and compared the experimental data with an 'integrated red cell model', which seeks mathematically to model the osmotic behaviour of red cells under different conditions. Upon experiment, lysis in these cells was reduced by additives that could be regarded as impermeant extracellular solutes (citrate, mannitol) and by low pH, but not by those agents that are regarded as protecting the cell against energy depletion or oxidation (adenine, glucose, nicotinic acid). The protective effects of these extracellular additives were all reproduced by the computer simulation, confirming the validity of this model, although the effect of pH could be simulated only semi-quantitatively, possibly because Na+ permeability itself depends on pH.