The alterations of atrial structure induced by the iterative atrial fibrillation (AFib) include renin-angiotensin-aldosterone system (RAAS) overexpression which could have a dominant role, aldosterone being involved in inflammation, fibrosis, remodeling. The objective of our study is the direct comparison of two therapeutic regimens (each one including other three subregimens), in order to assess the benefit of mineralocorticoid receptor blockers with spironolactone (S) in repetitive AFib patients (pts). Method. The study considered retrospectively 1008 pts with AFib during the last seven years, structured into two comparative groups, demographically balanced (slight male and 6th decade pts predominance, respectively, in both groups). The pts within the first group were treated with antiarrhythmics [Amiodarone (A), Propafenone (P) or Sotalol (So)] + S, while the pts within the comparative group were treated with antiarrhythmics (A, P, So) + exogenous potassium supplement (K+). We compared the occurrence of AFib episodes 24 months before and, respectively, after the initiation of treatment with S. Among the exclusion criteria we notice the pts previously treated with betablockers (indirect antireninic effect), and ACE-inhibitors or ARB’s (K+ suppliers), respectively. Results. In the therapeutic arm with antiarrhythmic + S, the AFib episodes decreased dramatically over two times within the two time intervals taken into consideration. In contrast, within the therapeutic arm with antiarrhythmic + K+, the AFib episodes slightly increased. Conclusions. According to our results, S seems to be a valuable additional therapeutic tool in prevention AFib recurrences. Beyond, S reduces RAAS activity and could also reduce the fibrosis involved in structural remodelling. These beneficial effects were independent of blood pressure lowering and are probably connected to the antiinflammatory effects of S.