The distribution and the biological half-lives of 137Cs in poultry after continuous intake of foodstuffs contaminated by the Chernobyl fallout were studied in order to determine transfer coefficients to yolk, albumen, and shell of eggs as well as transfer coefficients to chicken meat. Mean values for laying hens were found to be 0.2 d kg-1 (whole consumable egg), 1.2 d kg-1 (leg meat), and 1.6 d kg-1 (breast meat) when radiocesium was fed in contaminated grass pellets, and about twice as large [i.e., 0.4 d kg- 1 (whole consumable egg), 2.8 d kg-1 (leg meat), and 3.0 d kg-1 (breast meat)] when radiocesium was fed in contaminated wheat. Reducing effects of the feed additive ammonium-ferric-cyano-ferrate in concentrations of 0.66 g kg-1 of feed mixture on the contamination of hen products were quantified to be a factor of 3 to 4 (whole consumable egg and meat after grass pellet feeding) and 8 to 14 (whole consumable egg and meat after wheat feeding). A drastically higher reduction with an ammonium-ferric-cyanoferrate dose twice as large (1.33 g kg-1) was achieved. For broiler chickens, activity concentration ratios of meat to feed were derived for various fattening periods, with mean values of about 0.3 (leg), 0.4 (breast), and 0.2 (liver). The addition of ammonium-ferric-cyano-ferrate reduced the activity concentrations in meat by factors of more than 6.