[en] Calculational models for evaluation of external dose due to a gamma plume are reviewed. Polynomial approximations of dose-buildup-factor are examined.It is difficult to evaluate accuracies of models from those of components being used in them. Comparisons between calculated doses and observed ones around BWR sites usually show agreements within a factor of two. As a new technique for predicting concentration distribution, PIC model is mentioned. Regional tracer studies using ¹³¹I and ⁴¹Ar show that 60% of the time agreement between the model and field data was within a factor of two. (auth.)