Diuretics are agents that increase urine output or flow. The effects of diuretic agents on electrolyte and water excretion in the kidney for the treatment of edema, congestive heart failure, ascites, and hypertension are reviewed. The structure and function of the kidney in the formation of urine are presented using the functional unit of the kidney, the nephron. The various sites where absorption, secretion, and the passive and active transport of water and electrolytes alter the composition of the glomerular filtrate from Bowman's capsule as it passes through the lumen of the nephron to the collecting ducts on its way to becoming urine are described. Diuretics are classified as low ceiling, high ceiling (loop), and potassium‐sparing diuretics, natriuretic peptides, atrial natriuretic peptides, atrial natriuretic peptide potentiators, osmotic diuretics, carbonic anhydrase inhibitors, methylxanthines, organomercurials, and aquaretics. The pharmacology, mechanisms or site of action in the nephron, and clinical effectiveness are discussed. Included is a discussion of the risk factors and side effects of diuretic agents.