Wilms' Tumors (A histopathological evaluation of 103 cases): 103 Wilms'tumor cases were examined in this study. 96 of them were seen in childhood and 7 were seen in adults. It was seen that Wilms' tumors, with a percent of 18.7, took the 3rd place in frequency among all of the primary malignant renal tumors (which were 551 cases). The mean age was accounted as 5.5 for all cases and 3.5 for childhood.37 % of the cases were under 2 years of age while 79 % were under 5 years. 44 % of the cases were females while 56 % were males. In histopathological examination it was seen that 62 % of the cases were classical triphasic, 23 % were dominantly blastomatous, 10 % had anaplastic features and 8 % had shown partially cellular differantiation according to the classification. Among the ten cases which were accepted as inappropriated group, anaplasia was diffuse in nine. 9 of these 10 cases were above 2 years of age. Histopathological evaluation of Wilms' tumors according to anaplasia and variants showing differences is important in the therapeutic and prognostic factors.