Fluid and electrolyte imbalance constitute an important part of USMLE testing. And to ace it, is required a very thorough understanding of the intricacies of the homeostasis mechanisms. Therefore special attention has been given to this area of Nephrology in this chapter. Notable topics in this chapter include Hyponatremia, Hypernatremia, Hypokalemia, Hyperkalemia, Anion Gap, Acid-Base disturbance, Renal Tubular Acidosis (RTA), Acute Kidney Failure (ARF), Acute Kidney Injury (AKI), Nephritis, Glomerulonephritis, IgA Nephropathy, NSAIDs induced Nephropathy, Goodpasture syndrome, Nephrotic Syndrome, End Stage Renal Disease (ESRD), Chronic Renal Failure (CRF), Dialysis, Hypertension (HTN), Nephrolithiasis, Diuretics, Genitourinary Tumors. Few of the quick reference tools in this chapter include Acid-Base disturbance, RTA differential, Urine Analysis table, Secondary causes of HTN, Renal stones, Renal pharmacology with indications, contraindications and adverse effects.