OBJECTIVES: The financial burden of kidney transplantation depends on many variables as the age of patients, available complications, success rate, introduction of new medicines etc.   The objective is to analyze the pharmacotherapy cost of patients with kidney transplantation in Bulgaria during 2006 – 2009. METHODS: It was collected information for all patients with kidney transplantation during 2006 -2009. Out of 523 transplantated patients (n=520) were included in the observation. The patient sample was systematized according to patient age, gender, medicines used for main and supporting therapy, monthly and yearly cost of pharmacotherapy. RESULTS: Thirty-six percent (n=189) are female and 64% (n=331) are male. Prevailing part of patients are among 31 to 50 years old (n=264; 51%). Below 20 years are 7 patients and up to 70 years are 6 ones. The standard therapy includes a combination of immunosuppressants. In the prevailing part of the patients were prescribes ciclosporin A or sirolimus in combination with azathioprine or mycophenolic acid. In case of allograft rejection the thymoglobulin is used and in case of HBV infection is used lamivudine. The CMV therapy is performed with gancyclovir. The monthly cost of therapy during the first year of observation is varying among 8.29 – €1276 for 354 of the patients, while the monthly cost at the end of the period was 9.08 – €931.81 for €374 of the patients. The yearly cost of pharmacotherapy was found to vary on average from 3973 to 4325 per treated patient but the drop out level was high. CONCLUSIONS: Most of the modern medicines have been found prescribed in the collected sample with a tendency for new medicines inclusion early after their market launch. The main dominants of the pharmacotherapy cost changes are the availability of infections, followed by the kidney rejection risk, and new medicines appearance on the local market.