Urinary proteins are heterogeneous and increased urinary protein excretion is associated with renal pathology. The quantitative and qualitative composition of the proteins in the urine carries diagnostic value. Urinary N-acetyl-β-D-glucosaminidase is of renal origin. The activity of this enzyme is high in renal proximal tubular cells, and when proximal tubular cells are injured by disease or nephrotoxic agents, urinary level of this enzyme increases. In this review, disease states, drugs and toxins causing changes in the urine level of this enzyme are discussed.