BACKGROUND: Iron deficiency is common in patients with chronic kidney disease and in kidney transplant recipients. PATIENTS AND METHODS: We analyzed the safety and tolerability of the new intravenous iron preparation ferric carboxymaltose (FCM) in these two patient groups. Adverse events after administration of the drug were assessed by using a questionnaire. Vital signs and laboratory data were collected before and after the application of FCM. A total of 46 FCM doses were applied to 44 patients (17 with chronic kidney disease and 27 kidney transplant recipients) either as single injection of 100 or 200 mg (n = 42) or as short infusion with up to 500 mg (n = 4). RESULTS: Mild and transient adverse events (metallic taste, headache, dizziness) occurred in six patients. The estimated glomerular filtration rate remained unchanged by the FCM administration. CONCLUSION: We conclude that safety and tolerability of FCM were excellent. Compared with other intravenous iron preparations the considerably shorter administration time of FCM allows to save time and to reduce costs.