Loss of heterozygosity (LOH) was studied in 10 primary retinoblastoma tumors in the VNTR region of intron 1 in p53 gene by the polymerase chain reaction. To our knowledge mutations have not been reported in the p53 gene in retinoblastoma primary tumors. Heterozygosity was found at this region in 5 of 10 cases. Two pathology paraffin block samples showed loss of heterozygosity.