Abstract: A "high risk" nasopharyngeal cancer family was studied for the chromosome aberrations by peripheral lymphocyte culture with TC 199 medium of low folic acid and G—banding technique. The average chromosome aberration rates (CAR) of the family and the control group were 11.1% and 5.06% respectively, there is a highly significant difference between them (P0.001). The CAR of spouse group was 4.6%, no statistical difference as compared with the control one (P0.25). The translocation (7; 14) (p22; q22) was observed twice in the non-affected member of the family. The data Obtained suggest. 1. some members in the family have an increased chromosome instablity, possibly predisposing to NPC; 2. more difference between CAR of the family and the control can be taken under this culture condition.