1. Erythropoietin (EPO) is a hormone regulating the proliferation and differentiation of erythroid precursor cells. The hypothesis that haematopoietic and endothelial cells share a common haemanglioblast progenitor among others is based on the finding that both cell lineages express cell surface antigens, such as CD31 and CD34. 2. In the present study, we investigated the angiogenic potential of recombinant human erythropoietin on cyclosporine A (CsA)-induced nephrotoxicity in the rat kidney and compared it with the effect of basic fibroblast growth factor (bFGF), a well-known angiogenic factor. 3. Rats were divided into five groups: A (control), B (EPO treated), C (CsA treated), D (CsA + EPO treated) and E (CsA + bFGF treated). Mouse anti-human CD31 and CD34 antibodies were used to evaluate the kidney vessels present in histological preparations. 4. Glomerular and peritubular capillaries in Group B (EPO) were increased compared with the control (Group A; P < 0.05). Reduction of the same kidney vessels (glomerular and peritubular capillaries) in Group C (CsA; P < 0.05) compared with controls was observed, whereas in Groups D (CsA + EPO treated) and E (CsA + bFGF treated), capillaries were increased compared with Group C (CsA; P < 0.05). 5. Erythropoietin has a significant angiogenic effect in rat kidney with CsA-induced nephrotoxicity, similar to the effect of the other angiogenic factor bFGF.