This work was conducted to study the effect of uninephrectomy on the structure and function of the remaining kidney.39 male albino rats were used, 9 as control group and 30 as experimental group to which right uninephrectomy was done. 3 of the 9 and10 of the 30 rats were sacrificed 1, 2 and 3 months after the operation. Serum creatinine was detected and kidney specimens were examined .The early changes were expressed as glomerular hypertrophy and sclerosis as well as tubular hypertrophy and hyperplasia. The later ones were glomerular fibrosis and atrophy, tubular atrophy and interstitial fibrosis despite normal serum creatinine level. It could be concluded that by time uninephrectomy represents an acceptable risk of progressive harm to the remaining kidney.