Some urinary enzymes and low molecular weight proteins have been used as early markers of kidney damage and useful for the detection of small changes in the function of tubular epithelial cells in many pathological conditions. Their excretions increase long before elevation of other markers of renal function, such as creatinine. The first part of this review describes the sources of urinary enzymes and proteins and discusses the preanalytical and analytical problems with estimation of enzymatic activity and protein levels in the urine, mainly the problem of quantitative expression of excretion of urinary enzymes. After the description of main characteristics of diagnostically most important enzymes and low molecule weight proteins excreted in the urine, the diagnostic validity of enzymuria and microproteinuria with acute tubular necrosis, diabetic nephropathy, kidney damage due to nephrotoxic substances and in early detection of the complications after kidney transplantation are discussed.