Retinoblastoma is a malignant tumor of the retina that occurs in children, usually before age five years. Loss or mutations of both alleles of the retinoblastoma gene RBI, localized to chromosome l3q/4.2, are required to develop the disease. This study was conducted to determine RBI mutations in twoVietnamese children with retinoblastoma. The promoter and whole coding region of RBI of two children with retinoblastoma were sequenced by Sanger sequencing. Two germline ftameshift mutations in RBI gene were detected from two retinoblastoma children. One is 1337-1338insTA heterozygous mutation identified in RB6 sample and another is 1450-1451delTA heterozygous mutation found in RB7 sample. The 1337-1338insTA mutation causes a frameshift at amino acid 447 and an early stop codon at amino acid 451 while the 1450145ldeiTA results in ammeshift at amino acid 484 and a stop codon at arninoacid 491. They are both pathological, heritable mutations. These finding provide important clues for genetic counseling and clinical management.