The influence of the size of the container on platelet concentrate storage at 20-24 degrees C was examined. Baseline studies were obtained with 50 platelet concentrates in 300-ml PL-146 plastic containers. Experimental studies included 6 platelet concentrates each in 300-, 600- and 2,000-ml containers made of PL-146 plastic. Platelet count, total platelets, pO2, pCO2, pH, glucose consumption, lactate production, platelet morphology and recovery by platelets to osmotic stress were monitored during storage. During storage, the best pH and morphology values were observed with 2,000-ml containers. The lowest glucose consumption and lactate production were also associated with the 2,000-ml containers. Intermediate improvement in these parameters was noted in 600-ml containers. Recovery from osmotic stress was better in 2,000- and 600-ml containers as compared to 300-ml containers. In addition, characteristic changes in pO2 and pCO2 during storage suggest that improved platelet preservation in larger containers is due to improved gas exchange conditions obtained with increased surface area available for gas exchange.