Abstract: A method for the recovery of carbon-14 (C-14) from a mixture of inert gas and carbon-12 (C-12), carbon-13 (C-13) and C-14 dioxides. The mixture is cooled to a temperature below the solidification point of carbon dioxide to obtain solid carbon dioxide. The solid carbon dioxide is volatilized to provide substantially pure carbon dioxide gas which is reduced to carbon monoxide gas by reaction with metal. The carbon monoxide gas is cooled to obtain liquefied carbon monoxide. A feed of the liquefied carbon monoxide is subjected to fractional distillation and a bottoms rich in C-14 monoxide and poor in C-12 monoxide is collected and a distillate poor in C-14 monoxide and rich in C-12 monoxide is removed. The bottoms are oxidized to carbon dioxide rich in C-14 dioxide which is absorbed in a metal hydroxide solution and a carbonate salt rich in C-14 is obtained.