Objective To increase the statistic power to estimate radiation-induced cancer risk on the basis of analysis of the 1999-2002 follow-up data from high background radiation areas (HBRA), in combination with those in the period 1979-1998, and further to estimate radiation-induced cancer risk at low dose after adjustment of individual smoking factor.Methods Cohort studies were conducted of cancer mortality for the residents in both HBRA and control area (CA), with follow-up made in phases.The present study was first focused on the collection of cancer mortality data during 1999-2002, with preliminary analysis of the risks of cancer mortality.And then, the effort was dedicated to analysis of both the risks of cancer mortality and the smoker-adjusted risks of radiation-induced cancer mortality from for the residents in HBRA in period 1999-2002 based on the pooled data during 1999-2002 and 1979-1998 through ID record linkage.Person-years were estimated using Epicure/DATAB model.The relative risk (RR), the excess relative risk coefficient (ERR/Sv) and confidence interval (CI) of cancer mortality from 1979 to 2002 were estimated using Poisson regress model in AMFIT mode.Results A total of 76 264 persons in HBRA and CA was followed up during 1999-2002, covering 300 523 person-years and 2 267 deaths identified, including 239 cancer deaths.Based on pooled data, 125 079 persons were followed up during 1979-2002, which covered 2 293 463 person-years and 14 711 deaths identified, including 1 441 died of cancer.The sex-and age-adjusted RR of all cancers in the HBRA during 1979-2002 was 0.99 (95％ CI: 0.89 to 1.11), showing no statistically significant differences between HBRA and CA (P ＞ 0.05).The value of ERR/Sv of all cancer mortality during 1979-2002 was-0.01 (95％ CI:-0.50 to 0.64).Smoker-adjusted RR of all cancer mortality in HBRA during 1987-2002 was 1.00 (95％ CI:0.87 to 1.15), with no statistically significant difference (P ＞ 0.05).The value of ERR/Sv for all cancers during 1987-2002 was 0.01 (95％ CI:-0.56 to 0.81) after adjustment of smoking.Conclusions Increased risk was not found in relation to radiation exposure at low dose in HBRA.After adjustment of smoking, the statistical difference has not been shown in all cancer mortality between HBRA and CA, but excess relative risk increased slightly.