Post-transplant diabetes mellitus (PTDM) is a common complication after orthotopic liver transplantation (oLT). In our study, we investigated the prevalence and risk factors one year after transplantation in 618 patients who underwent oLT between 1990 and 1996 in a single center. The influence of steroid medication and hepatitis B or C (HBV/HCV) was also studied. Before oLT 66 of the 618 patients were diabetic. After transplantation 37 of these 66 (56%) patients showed no further signs of DM. Of the 552 patients without DM before transplantation 39 (7.2%) developed new onset PTDM. There was no influence of steroid medication on the presence of PTDM (steroids 10.4% PTDM, no steroids 12.5% PTDM). In addition we found no influence of HBV or HCV-infection on PTDM development. Analysis for risk factors showed no significant influence of the diagnosis leading to oLT, of FK506 or Cyclosorin A medication, age, gender or Child-Pugh class. Five year patient survival was not influenced by the presence of PTDM, especially patients with a preexisting DM showed no reduced survival. However, a subgroup of patients with new onset insulin-requiring PTDM showed significantly reduced 5 year survival (p<0.05). In conclusion we found new onset PTDM in 7.2% of patients undergoing oLT one year after the operation. On the other hand in more than 50% of patients with preexisting DM, the disease was no longer present post-transplant. This could be an indication that DM is dependent on liver function in these patients. Patients with preexisting DM should not be excluded from transplantation if indicated. Development of new onset insulin-requiring PTDM could be an important prognostic factor for patient survival after oLT. Further investigations are necessary to evaluate the prognostic meaning of PTDM and the pathophysiologic mechanisms.