An overview is given about the different variables which are of influence during platelet storage. After reinfusion of 51Cr-labeled platelets of PRP stored in first generation containers and evaluation of in vivo recovery and half life optimum, range of storage temperature was found to be 20-24 degrees C. Storage of PC in first generation containers showed a significant fall of pH which was in a clear relationship to platelet concentration, lactate production, and glucose consumption. If pH fell below 6.0 irreversible morphological changes and decrease of in vivo recovery/survival was observed. The second generation containers (PL-732, CLX, PL-1240) resulted in superior pH maintenance which was due to superior O2 and CO2 transport through the walls of the bags and a lower rate of glycolysis. In vivo recovery showed a gradual decline from 57% for fresh platelets to 42% after 7-day-storage. Platelet survival curves after 7-day-storage lay just at the lower limit of the range for fresh platelets. The success of prolonged storage depends critically on the mode of agitation used which was demonstrated by comparing three different agitators. A lot of questions remain still to be answered concerning the substrates of the oxidative metabolism, the morphological changes, and especially the in vitro function of platelets after prolonged storage.