Interlaboratory inspection of the quality of laboratory investigations in the Saratov region, carried out in 1987-1988, has revealed a 9 to 50 percent share of unsatisfactory results of measurements of urinary protein by the Roberts-Stolnikov method. This fault was not mended despite the measures taken and the errors detected in the activities of clinical diagnostic laboratories. Analysis of the relevant literature has led the authors to a conclusion that the biuret method, the most specific and sensitive of all the universal methods, should be given preference to. The final stage of the investigation is carried out with the use of a KFK-2M photoelectrocolorimeter. A standard curve based on albumin calibration solution was plotted to estimate the results. At present 15 clinical diagnostic laboratories of this region are using the biuret method. Their results have improved, as evidenced by interlaboratory quality control: the share of satisfactory results of urinary protein measurements makes up 83 to 100 percent.