Objective. Studied kidney functiona and urinary syndrome after using Diclofenac and Celecoxib in patients with oxalate nephropathy with primary gonarthrosis. Methods. We examined 51 women 45-60 years old, who suffered from oxalate nephropathy for more than 20 years with chronic kidney disease 1-2 stage with a glomerular filtration rate (GFR) of not less than 60 ml/min. Patients of the 1st group (22 people) took diclofenac sodium (course dose of 3000 mg) for a month, patients of the 2nd group (29 people) took celecoxib (course dose 6000 mg). Assessed GFR in dynamics, uric acid clearance and urinary syndrome (before treatment, on the 30th day of treatment, and a month after the drugs dechallenge). Results. By the 30th day of treatment with diclofenac, nephrotoxic effects were observed, characterized by a statistically significant decrease in GFR (from 89.0±9.1 to 57.5±2.9 ml/min) and uric acid clearance (from 5.2±9.1 to 4.1±0.4 ml/min). Microscopy of urine sediment showed an increase in aggregation of calcium oxalates, the appearance of microhematuria and proteinuria. Celecoxib by this time led to a moderate decrease in GFR (from 85.5±8.2 to 61.2±9.3 ml/min), but did not cause changes in the clearance of uric acid and urinary sediment. A month after the drugs dechallenge, all the indicators returned to their original level. Conclusions. Celecoxib demonstrated less nephrotoxicity than diclofenac. The latter caused an exacerbation of nephropathy, an increase in oxalate-calcium crystalluria, the appearance of microhematuria and proteinuria. Celecoxib only reduced the rate of glomerular filtration, without causing changes in urinary sediment.