Previous work established that the flow cytometric dihydrorhodamine (DHR)- based assay for evaluation of oxidative burst is a sensitive method for evaluating phagocytes in patients with possible chronic granulomatous disease (CGD). It has also been useful as an accurate test for screening possible X-linked CGD carriers. This assay also is a good screen for the genotype of the disease. The method was optimized and is sensitive to 1 normal cell in less than or equal to 10,000 abnormal cells. Because of this sensitivity, this method has been extended to track granulocytes post-transfusion in CGD patients following allogeneic leukocyte transfusions. Pre-transfusion and l-hr, 6-hr, and 24-hr post-transfusion DHR tests are being performed in these patients, and data are being compared to other measures of cell survival, clinical status, and circulating cell numbers.