Abstract. The polarographic behaviour of spironolactone in Britton-Robinson buffers containing 40~ methanol as a solubilizer was studied. Over the pH range 3-12 a cathodic wave was produced. The wave was characterized as irreversible, diffusion-controlled and partially affected by adsorption phenomena. The number of electrons involved in the reduction was found by coulometric measurements at a controlled potential. A method was developed for the determination of spironolactone in tablets and the results obtained were in agreement with those obtained by the B.P. 1988 method. The mechanism of the electrode reaction is discussed.Key words: spironolactone, polarography, dosagi forms, pharmaceutical analysis Spironolactone is a steroid that acts as a competitive antagonist of the endogenous mineralocorticoid aldosterone. It is indicated in the treatment of essential hypertention, oedema associated with congestive heart failure, hepatic cirrhosis with ascites, the nephroti¢ syndrome and idiopathic oedema. By blocking the sodiumretaining effects of aldosterone, spironolactone corrects one of the most important mechanisms responsible for the production of oedema. It is rapidly metabolised after oral administration. The metabolites are excreted largely in the urine, but also in the bile [1].As a result of the widespread therapeutic use of spironolactone, much attention has been paid to its determination either alone or in combination with other drugs or metabolites. The USP XXII [2] recommends HPLC for the determination of spironolactone whether alone or in combination with hydrochlorothiazide. On the other hand, the B.P. 1988 [3] describes a direct spectrophotometric method. Other methods reported include spectrophotometry [-4-8], fluorimetry [9][10][11], TLC [12,13], HPLC [14][15][16][17] and GC-MS [18,19], but no polarographic studies seem to have been made hitherto.