We determined total blood protein (TBP) and total urine protein (TUP) in healthy subjects and urolithiasis (UL) patients with renal calculi of different chemical composition: phosphate (CaP), oxalate (CaOx) and urate (HUr). We discussed the peculiarities of TBP and TUP distribution curves obtained and showed that the data on TBP and TUP do not make it possible to reliably single out patients with UL or determine the chemical composition of calculi in their kidneys. However, it was established that the comparison of TUP measurement results for UL patients using the Ponseau-S and sulfosalicylic acid methods makes it possible to reliably separate patients with Ca-containing calculi (CaP and CaOx) from those with HUr calculi. The explanation to this phenomenon using the data on the fractional composition of TUP and the organic matrix of those patients’ calculi is given.