The microbial contamination of platelet concentrates (PCs) prepared by two different methods both with a high risk of bacterial contamination during preparation and storage were evaluated. For apheresis platelets, the concentrates were obtained using the Haemonetics MCS 3P device. For the random method, platelets were obtained by two phase centrifugation, in the Heraeus Cryofuge 8500 I device using the Kansuk 3-way bags which permit storage for five days. 1620 platelet pheresis units prepared by apheresis, and 9838 units prepared by the random method, were included in the study. Of the 11,458 PCs studied, 32 (0.27%) were false positives and 24 (0.2%) were real positives. All of the positive results occurred in platelets prepared by the random method. C. xerosis and S. epidermidis, S. hominis, Alpha-hemolytic streptococci, all flora of the skin, were isolated in the contaminated concentrates. The risk of microbial contamination of PCs, prepared both by apheresis and from whole blood, continues at a low rate although the products were collected into specific bags following rules including appropriate disinfection of the skin, correct centrifugation collection time and optimal storage conditions including temperature and agitation. These results again emphasize the importance of. obeying phlebotomy rules and hand disinfection of the person who collects the blood as well as the need for careful skin decontamination of the donor, during donation. (C) 2001 Elsevier Science Ltd. All rights reserved.