Herein is presented the development and therapeutic use of diuretic agents, a topic that constitutes one of the most significant advances in medicine made during the twentieth century. Diuretics are among the most frequently prescribed therapeutic agents for the treatment of edema, hypertension, and congestive heart failure and they act primarily by inhibiting the reabsorption of sodium ions from the renal tubules in the kidney. Recent advances in renal and ion‐transport research have led to a more precise understanding of the cellular mechanisms of actions of the various classes of diuretic agents. This understanding has aided the design of newer and more effective agents. Today diuretics are grouped as loop, potassium‐sparing, thiazide, or osmotic diuretics and include compounds that have combined diuretic and uricosuric properties. Uricosuric agents increase the excretion of uric acid, a principal product of purine metabolism; and because hyperuricemia is an adverse effect sometimes observed with diuretic treatment, arising from decreased extracellular volume and increased urate reabsorption, this combined property is advantageous. However, given that diuretics themselv are convenient, inexpensive, and generally are well tolerated, they will probably continue to play a role in the treatment of hypertension.