Post-transplant hospitalizations of kidney transplant recipients, especially if of long duration, impose extra costs on health system by occupying hospital beds and using human resources. We designed a study to identify the leading high-cost hospitalizations of these subjects and compare the duration of hospital stay for each etiology. In a retrospective review in Baqiyatallah Hospital from 2000 to 2005, from 342 hospitalizations of kidney recipients after transplantation, five most expensive causes of hospitalization were identified were studied. Mean costs (in US dollars) and duration of hospital stay were determined and compared among five high-cost causes. The five most high-cost etiologies of hospitalization in decreasing order were as follows: ischemic heart disease, IHD, ($1175±989), cerebrovascular accident, CVA, ($1153±1266), nephrolithiasis ($653±776), existing diabetes mellitus ($647±561) and cholestasis ($636±568). Mean hospital stays for these etiologies in decreasing order were as follows: 14±8 days for diabetes, 11±9 days for CVA, 8±5 days for cholestasis, 7±4 days for IHD and 7±6 days for nephrolithiasis. Among five high-costly causes of hospitalization during post-transplantation phase, uncontrolled diabetes and CVA account for more occupation of hospital beds and use of human resources. Most of the costs of IHD, biliary stone and cholestasis are associated with interventional procedures and not hospital stay.