Comprehensive results from miners cohorts have demonstrated a clear association between lung cancer risk and radon exposure cumulated during occupational life. However a large proportion of these miners had cumulated high radon exposure during a short period. The French and Czech cohorts of uranium miners allow to analyse the potential risk linked to low radon exposures protracted over long duration. Furthermore, the study will allow to consider the modifying effects of other factors present in the mining atmosphere. The present analysis is based on 5098 miners employed in French uranium mines for at least one year since 1945, and followed up to 1994. A total of 5002 Czech miners employed since 1952 have been followed up to 1995. Mean cumulative exposures are 36 and 57 WLM among French and Czech miners, respectively, protracted in average over 11 and 10 years. A significant excess of lung cancer deaths is observed in both cohorts. A linear association of this risk with cumulative exposure to radon was confirmed. he purpose of the joint analysis is to study the influence of low annual exposures (exposure rate effect). According to these analyses, the occupational exposure gives the opportunity to evaluate lung cancer risk for annual exposures to radon in the range of 2 WLM or less, the levels that are comparable to exposures of about 400-500Bq/m3 in dwellings.