Experimental studies have demonstrated that calcium is an essential molecule in modulation of erytropoiesis. The aim of this study was to investigate the role of serum calcium levels on the development of post-transplant erythrocytosis (PTE) in renal transplant recipients. We enrolled 155 patients (36F/119M, mean age 34.9±9.7 years) with normal graft function who underwent renal transplantation between 1999 and 2002. All of the patients; demographic features and various laboratory parameters were analyzed as the possible factors associated with erythrocytosis. PTE was appeared in 43 (27.7%) patients during the follow-up period. Sixty-three (40.6%) patients developed hypercalcemia (corrected serum calcium level >=10.2 mg/dl). Serum calcium levels tented to increase in patients with PTE, but significantly decreased in patients without PTE (10.6±0.6 vs. 9.8±0.5 mg/dl, p=0.000). Similarly, hypercalcemia was more common in patients with PTE compared with patients without PTE (74.4% vs. 27.7%, p=0.000). Hypercalcemic patients had a significantly higher frequency of PTE than normocalcemic patients (50.7% vs. 11.9%, p=0.000). There were no differences in other laboratory and demographic data between the patients with hypercalcemia and PTE (p>0.05). These findings suggest that hypercalcemia may lead to increased post-transplant erytropoiesis in renal transplant recipients.