en Medical Genetics Medical Genetics Original Research Original Research <strong>Background: </strong>Bladder cancer is the most frequent malignancy that affects the urinary tract. Studies have shown different types of FGFR3 and HRAS genes mutations in human bladder cancer, with a comprehensive range of mutation number in various populations. This study aimed to determine the specific point mutations of these 2 genes among Iranian patients with bladder cancer.<br> &nbsp;&nbsp; <strong>Methods:</strong> In this study, 100 specimens of patients with transitional cell carcinoma were analyzed.&nbsp; All samples were examined for FGFR3 and HRAS mutations using PCR and direct DNA sequencing methods.<br> &nbsp;&nbsp; <strong>Results:</strong> A total of 9 pathogenic mutations and 9 polymorphisms were found in 2 exons (7 and 15) of the FGFR3 genes in patients with bladder cancer (S249Y, I633I, L645L, D646E, Y647*, D628V, P250T, Q263H, Y305H). However, no mutation was found in exon 10 of FGFR3 and exon 1 of HRAS genes.<br> &nbsp;&nbsp; <strong>Conclusion:</strong> In this study, 5 mutations were found in FGFR3 gene that have not been detected previously. There was no mutation in exon 10 of FGFR3 and exon1 of HRAS. The results of this study confirmed the association of ethnic-genetic factors in the occurrence of bladder cancer, so that these variables may not be present in all ethnic groups.<br> &nbsp; TCC, FGFR3, HRAS, FFPE, Touch down PCR 741 746 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-3949-1&slc_lang=en&sid=1 Ameneh Homami amena.hilli@yahoo.com 200319475328460064307 200319475328460064307 No Department of Medical Genetics and Molecular Biology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran Zohreh Ataei Kachoei abc1349@yahoo.com 200319475328460064308 200319475328460064308 No Department of Medical Genetics and Molecular Biology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran Mojgan Asgarie mojgan_asgari@yahoo.com 200319475328460064309 200319475328460064309 No Department of Medical Pathology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran Farideh Ghazi Ghazi.f@iums.ac.ir 200319475328460064310 200319475328460064310 Yes Department of Medical Genetics and Molecular Biology, School of Medicine, Iran University of Medical Sciences, Tehran, Iran