To assess the viability of human red blood cells that have been lyophilized and reconstituted to the hydrated state, we phlebotomized a unit of whole blood from six healthy male volunteers. Their packed red blood cells were lyophilized at -40 degrees C and stored at 4 degrees C. Upon rehydration, recovery of erythrocytes was 85.2 +/- 2.79%. Aliquots of 20 ml were labeled with 51Cr and re-infused into the original donors for red cell survival studies. The red cells retained ABO and Rh identity upon rehydration. There were no adverse clinical affects of re-infusion. The half time of 51Cr disappearance from the circulation was 31 +/- 8.19 days, and there was no evidence of significant splenic sequestration on the day of reinfusion. Red cell indices of the rehydrated erythrocytes were normal, oxyhemoglobin content was 98.58 +/- 1.46%, and P50 was 27.25 +/- 1.84 mmHg. Although deformability was slightly decreased, the osmotic fragility and filterability of the red cells were normal. These data demonstrate that human erythrocytes can be lyophilized and reconstituted to the hydrated state and survive normally in the circulation. Metabolic, osmotic, hematological and rheological function remains intact.