Lesions of kidney are the situation that it can failure and decrease the function of kidney as accumulation of uric acid (urinary nitrogen) in blood and body fluids. Subsequently, the uric acid as urate crystal can precipitate in different part of body. This study was carried out in 2014, in Isfahan province. After identification and history taking, the samples were taking from the chickens with 30-40 age weeks that dead during one week. After examination and necropsy of carcasses, the carcasses that have macroscopic lesions in kidney were sampled from kidney. In this study, from 500 samples, the microscopic lesions of kidney were been in 40% of samples that including of 21 samples by pyelonephritis, 74 samples by glomeronephritis, 105 samples by interstitial nephritis, 5 samples by interstitial nephritis and pyelonephritis and 2 samples by glomeronephritis and pyelonephritis, simultaneously. All samples have urate precipitation and some chickens have kidney stones. Results show that the highest nephropathy in studied flocks was interstitial nephritis. The chickens that were infected to infectious bronchitis in growing period have higher mortality than others. This study shows that the kidney lesions are one of main factor in decreasing of production and mortality of chickens in this flocks.