When a commercially available intravenous solution, plasmalyte‐A, was added to platelet pellets as a platelet storage medium (PSM) after more than 85 percent of the plasma had been expressed, the platelets functioned equally well, after 5 days of storage, in platelet aggregation, release reaction, and serotonin uptake as did platelets stored in plasma. The level of fibrinopeptide A was significantly different in the PSM. Similarly, lower levels of kallikrein and complement components in the PSM‐stored platelets indicated reduced activation of plasma enzyme systems. Morphology scores showed better shape maintenance in PSM, with values of 255 versus values of 185 in plasma (time zero, 280); electron microscopy also showed somewhat better structural maintenance in PSM. Glucose consumption, lactate and ammonia production, and fatty acid oxidation were also reduced in PSM. No significant differences in pH, white cell count, pO2, pCO2, or lactic dehydrogenase were observed after 5 days of storage in plasma or PSM; however, platelet counts were reduced after 5 days in plasma but remained constant in PSM. The beta‐thromboglobulin release was significantly lower in the PSM‐stored platelets after 5 days. The volume of platelet membrane glycoprotein lb (which is responsible for platelet adhesion) decreased 15 percent in plasma following storage, whereas a decrease of only 5 percent was noted in PSM. There was less leaching of plasticizers in PSM than in plasma. Survival and recovery using 51Cr‐labeled autologous platelets showed that, after 5 days of storage, the recovery of PSM‐stored platelets was 63 percent and the survival was 7.7 +/− 0.8 days (multiple hit model) The data support the hypothesis that plasma is not necessary for the storage of platelet concentrates and that removal of the plasma may benefit by removing enzymes systems that effect the biochemical alterations that occur d