Hyaline casts are believed to be formed by precipitation in gel form of Tamm Horsfall (T-H) mucoprotein, secreted by the ascending limb of the Henle’s loop and the distal renal tubule of a glomerulus, with plasma protein (mainly albumin) in the urine. However, the presence of the T-H mucoprotein and albumin in the urine alone does not give rise to hyaline casts. Four conditions are now known to be necessary conditions for the formation of hyaline casts. These are: (1) Lowered urine pH, (2) Increased plasma protein in the urine, (3) Concentration of urine, and (4) Lowered urine flow.