The present study was intended to examine the stability of amiodarone (Cordarex(R), CAS 1951-25-3) and it's metabolite desethylamiodarone. For this purpose 20 ml of blood were taken from each of 12 patients treated with amiodarone and were stored, after centrifuging, at room temperature, + 5-degrees-C, - 18-degrees-C and - 38-degrees-C The amiodarone and desethylamiodarone concentrations were determined by the HPLC method 30 min, 24 h, 48 h, 72 h, one and two weeks after blood-taking It turned out that the serum levels decreased continuously as of the first day regardless of the storage temperature. Correction factors were therefore calculated for the amiodarone concentration.- if the blood level determination takes place after 24 h one should add 8 % to the obtained value, a ter 48 h 16 %, after 72 h 19 %, after one week 23 % and after two weeks 32 %.