[en] Associations of smoking habit with serum levels of total protein as well as protein fractions were studied in a population consisting of 4,739 atomic bomb survivors and unexposed control subjects in Hiroshima who participated in the 1979-81 period of the Adult Health Study, an on-going health follow-up program of the RERF. Smoking was strongly related to serum protein concentration after correction for age, sex, and body mass index. Among current smokers as compared to nonsmokers, levels of total protein, β globulin, and γ globulin were significantly lower (p<0.001), and levels of α₁ and α₂ globulin were significantly higher (p<0.001). For serum albumin levels, a decrease was also noted but it failed to attain statistical significance. Exsmokers were indistinguishable from nonsmokers in terms of the serum protein levels analyzed in this paper. With an increase in daily cigarette consumption, monotonic increases of serum levels were observed only in α₁ globulin. Duration of smoking (years) was related to increased α₁ and α₂ globulin. Smoking duration was also associated with albumin level but the trend was not monotonic. The radiation exposure effect on serum protein level was significant in several instances but was in general much smaller than the smoking effect. Its inclusion in the regression models did not noticeably affect the association between smoking and serum proteins. (author)