Recent numerous clinical studies have suggested that the renin-angiotensin-aldosterone system (RAAS) inhibitors have beneficial effects on hypertension, cardiovascular and chronic kidney diseases (CKD). Electrolyte disorder, especially hyperkalemia, is observed after the administration of RAAS inhibitors. This review focuses on the prevalence and severity of hyperkalemia with the use of RAAS inhibitors. Clinical evidences suggest that hypertensive patients with heart failure and CKD, and patients with combination treatment of RAAS inhibition are at higher risk of hyperkalemia, and serum potassium levels should be carefully monitored.