Urinary proteins measurements have basically been used for the diagnosis and monitoring of nephrourological diseases. The pattern of urinary protein excretion can be used to identify the cause of the disease and to classify proteinuria. Urine proteins testing usually involves a screening test to detect excess protein (dipstick, colorimetric or turbidimetric methods) at the beginning, a qualitative determination (electrophoresis with all its variants including immunofixation) and finally a quantitative evaluation (immunoassay). An especially important issue is the study of Bence Jones proteins - free monoclonal light chains – which are a significant marker of the malignant monoclonal gammopathy.