The results of irradiation experiments on spherical fuel elements in the Studsvik R2 and the Jülich FRJ2 reactors are used to derive release data for both gaseous and metallic fission products. Fission gas release follows the well-known dependence on the square root of half-life showing that diffusion is the controlling release process for both intact and failed particles. The release of 110mAg was generally about two orders of magnitude higher than that of 137Cs. Profile measurements indicate good retention of strontium. Results of the concentration profile and in-pile release measurements allow verification of data from out-of-pile experiments.