We have attempted a fine characterization of the angiogenic response induced by multiple myeloma endothelial cells (MMEC) by using the chick embryo chorioallantoic membrane (CAM) assay and by reverse transcriptase-polymerase chain reaction (RT-PCR). Results showed that in the CAM assay MMEC induced an angiogenic response comparable to that of a well-known angiogenic cytokine, namely fibroblast growth factor-2 (FGF-2), while RT-PCR demonstrated that the expression of endostatin mRNA detected in MM treated CAM was significantly lower respect to control CAM. These data suggest that angiogenic switch in MM may involve loss of an endogenous angiogenesis inhibitor, such as endostatin.