BACKGROUND: Recent researches have indicated that the generation and development of retinoblastoma(RB) might also be related with other anti-oncogenes except the known Rb1 gene.OBJECTIVE: To explore the loci of other genes which possibly participated in RB generation and development and try to find and confirm the indicators for the loss of heterozygosity(LOH) with merits in surveillance and prognosis.DESIGN: A case analysis by employing RB patients as subjects SETTING: A center of gene diagnosis and therapy of a military medical university-affiliated hospitalPARTICIPANTS: The study was conducted in the center of gene diagnosis and therapy of Xinan Hospital affiliated to Third Military Medical University of Chinese PLA. Sixteen RB cases including 10 males and 6 females were the patients of the outpatient department of three-affiliated hospitals of the Third Military Medical University of Chinese PLA from May 1998 to October 2001.Inclusion criteria: in accordance with RB diagnostic criteria and younger than 3 years old; Exclusion criteria: family heredity history. Two eyes were involved in 12 cases and one eye was involved in 4 cases.METHODS: Fourteen micro-satellite DNA labels on the 13th chromosome in tumor or peripheral blood samples were separately amplified by polymerase chain reaction(PCR) to analyze the incidence of LOH of each locus. Simultaneously, the genetic source of loci loss was confirmed by genealogical analysis.MAIN OUTCOME MEASURES: Frequency of LOH incidence on the 13th chromosome.RESULTS: In 16 RB patients,LOH occurred in one or more than one locus on the 13th chromosome of 12 cases. Thereinto, the probability of LOH occurrence on three loci including D13S265,D13S263 and D13S153(in Rb1gene) was the highest. Ten loci of LOH in 12 LOH positive samples were confirmed from agnate chromosomes. The RB confirmation of LOH-positive group or LOH-negative group needed 504 days or 1086 days,which was significantly different(t=2. 357,P<0.05).CONCLUSION: RB confirmation was earlier in LOH-positive patients than LOH-negative patients. Except the confirmed Rb1 gene, LOH on two loci including D13S263(13q14.1-14.2) and D13S265 (13q31-32) also might have certain suggestive effect on early intervention and functional surveillance of RB patients.