The pathophysiology of the single kidney is involved in the evolution toward endstage renal disease. Furthermore, most data suggest that the renal function of the donor is maintained after nephrectomy. This study sought to analyze the difference between surgically acquired single kidney and the congenital single kidney, regarding kidney function at a similar moment in time of the existence of a single kidney.Two groups were enrolled in this study. Group A consisted of 28 patients with surgically acquired single kidney, time from nephrectomy was 30.23 +/- 10.82 years; mean age, 54.42 +/- 14.99 years. Group B consisted of 20 patients with a congenital single kidney (mean age, 30.3 +/- 10.43 years). We assessed glomerular filtration rate (Modification of Diet in Renal Disease 4 Study Equation) and the presence of classic and nonclassic risk factors for chronic kidney disease.The estimated glomerular filtration rate showed no statistically significant difference between the 2 groups.Our study did not show any influence of surgical nephrectomy on the evolution of kidney function. Kidney function in the surgically acquired single kidney was similar to the kidney function in the congenital single kidney at a comparable time interval. Our results have potential favorable implications for kidney transplant from living donors.