The chemokine family consists of approximately 50 small (8–14 kDa), basic proteins that are expressed and released by a wide range of normal and malignant cells. Based on their molecular structure, these cytokines are divided into the two major subgroups CCL and CXCL chemokines that bind to CCR or CXCR receptors, respectively. These mediators are important for regulation of cell viability, proliferation, differentiation, and migration. Chemokines are important for cell migration during embryogenesis; they are involved in the regulation of complex processes like local recruitment of inflammatory cells, angiogenesis, and regulation of normal as well as leukemic hematopoiesis. Chemokines can be constitutively released by malignant hematopoietic cells as well as by bone marrow stromal cells. This bidirectional crosstalk between malignant hematopoietic cells and neighboring stromal cells may therefore be important for the development and clinical presentation of malignant diseases, and the chemokines or their receptors may also represent a target for specific anticancer therapy at the molecular level.