From a theoretical point of view, an alloimmune response can not take place, still some type of standard immunosuppression is used in about 60% of patients receiving kidney grafts from their monozygotic twins. We aimed at assessing clinical response in patients receiving renal grafts from a living monozygotic twin donor when no immunosuppressive therapy is used. METHODS: This is a retrospective observational study of patients receiving kidney grafts from their monozygotic twins from 1969 to 2013. The following data were recorded: age, renal graft recipient's primary disease, renal function, renal survival and overall survival. Immunosuppressive therapy included a single intraoperative dose of methylprednisolone 500 mg and no maintenance immunosuppression. RESULTS: Five patients with kidney grafts from their monozygotic twins were dentified in our centre. Mean age at transplantation was 33 years (27-39). One-year overall survival and graft survival were 100%. Mean creatinine level was 0.96 ± 0.2 one year after transplantation, and 1.2 ± 0.37 mg/dl at most recent follow-up. Two patients died with a functional graft more than 15 years after kidney transplantation (causes were melanoma and cardiovascular event respectively). Follow-up was lost in a patient one year after transplantation. Two patients are alive with a functioning graft at 18 months and 42.5 years after transplantation respectively. CONCLUSION: Kidney transplantation from a living monozygotic twin is associated to outstanding clinical outcomes. Immunossuppresive therapy to suppress alloimmune response in probably unnecessary 11 zygosity has been confirmed.