D-raf, Drosophila homolog of the human c-raf-1, serves as a central intermediate in many signaling pathways ultimately regulating cell proliferation, differentiation, and development. In transgenic larval tissues carrying D-raf and lacZ fusion gene, spatial patterns of D-raf gene expression have been reported in the fat body, the humoral immune tissue of insect. We investigated the possible role of D-raf in Drosophila immune response using Draf-lacZ transgenic flies and hypomorphic mutant D-rafC110 strain. Our results showed that expression of the D-raf gene was induced by injury or bacterial challenge, especially in fat body and D-raf may be involved in the process. And, the larvae of D-rafC110 strain showed abnormal hemocyte population and did not show the increased number of plasmatocytes nor the induced expression of the D-raf gene that detected in wild-type larvae after injury or bacterial challenge.