BACKGROUND: In January 2003, blood center personnel in the American Red Cross, Southern Region in Atlanta, noticed whitish particulate material (WPM) that had not been observed previously in several units of red blood cells (RBCs). An expert panel was formed to evaluate studies of the material and make appropriate recommendations STUDY DESIGN AND METHODS: The expert panel reviewed information provided by several investigations and organizations. This included: background information, and experiences relating to WPM; WPM composition; factors promoting WPM formation; risk of WPM (if any) to patients; and recommendations to prevent future occurrences. RESULTS: WPM is derived from blood. No data suggest that external contamination or collection set components contribute to WPM development. A major constituent of WPM is platelets (PLTs). WPM is most commonly observed in RBCs that have been subjected to a hard spin without PLT separation. WPM is rarely, if ever, observed in RBCs that have been subjected to leukoreduction. CONCLUSIONS: (1) WPM is not new, can be prevented, and can be removed. (2) WPM contains PLTs, white blood cells, fibrin, and cellular debris. (3) Changes in blood handling are not necessary. (4) WPM may be more frequent when higher g forces are used in component preparation. (5) Enhanced visual inspection of blood components need not be continued. (6) It appears that WPM may not form in RBC collected using automated devices. (7) WPM did not pose a risk to patients but should be avoided.