The evaluation of renal measurements such as length, width and thickness, volume is important in the diagnosis and treatment of many renal disorders, since there is a close relationship between the sizes of the kidneys and its function. The purpose of the study was to establish and compare during the postoperative period changes in the mass and sizes of the kidney left after nephrectomy in the sexually mature male rats. An experimental study was carried out on 84 sexually mature white male rats weighing 178-194 grams. Animals were divided into two groups: control (42 rats) and experimental (42 rats). In the control group, the animals under ketamine anesthesia were followed by an abdominal cavity dilution, after which the abdominal wall was applied in a row. All animals of the experimental group performed surgical intervention – nephrectomy of the left kidney. The animals were withdrawn from the trial by intra-pleural administration of thiopental-sodium 50 mg/kg after 7, 14, 21, 30, 90 days after nephrectomy. Macroscopic evaluation and description of the kidneys of animals was performed after their removal. Their weight was determined on the laboratory scale of HLR-200 up to 0.1 mg, and the length, width and thickness of the organ were measured with the help of a caliper to an accuracy of 0.05 mm. Calculated the volume of the kidney. The statistical analysis of the obtained results was carried out using the program STATISTICA 5.5 using parametric methods for evaluating the results. It was established that the mass, length, width, thickness and volume of the kidney of animals in the experimental group, as compared with the control group, were statistically significantly higher in all terms of observation. The fraction of the growth of the width and thickness of the single kidney of animals in the experimental group compared with the control animals in the animals was statistically significantly greater than the proportion of kidney growth during the postoperative period. It was found that the largest increase in the mass and thickness of the kidney, as compared with the control group, was observed after 30 days of the postoperative period, and the greatest increase in the length and width of the kidney, as compared with the control group, was observed after 14 days of the postoperative period.