Mercury is present in nature as metallic mercury, inorganic and organic compounds. Mercury levels constantly increase in the human natural environment. A similar rise of mercury content has been observed in human tissues. Kidney disease arising from exposure to heavy metals, mainly during occupational exposure to mercury, may play a special role in nephrology. Long-term exposure to mercury may cause progressive degenerative changes in the kidneys, possibly leading to renal insufficiency. The main renal changes caused by mercury are indicated by the both glomerular and tubular disfunction. Early renal damage may usually be monitored by measurements in urine excretion of very sensitive small proteins and of some enzymes. This article reviews data concerning the nephrotoxic effects of mercury compounds in animals and humans induced by exposure to mercury compounds with the results of our study in changes of proteins in urine excretion in groups of workers occupationally exposed to mercury vapours, (depending on degree and duration of exposure).