In mammals, FGFs constitute a large family of at least 18 growth factors. Their role in hematopoiesis is not well characterized. They may act upon cell proliferation or apoptosis, in conjunction with other, more specific, cytokines. Their receptors are integral molecules with tyrosine kinase activity, FGFR1 to R4. FGFR1 and FGFR3 have been recently implicated in the development of malignant hemopathies, such as a myeloproliferative disorder with t(6;8)(q27;p11), t(8;9)(p11;q32-34) or t(8;13)(p11;q12) and multiple myeloma with t(4;14)(p16;q32), respectively.