[en] Since 1975 I-129 has been measured in almost all solutions and in the exhaust air from the Karlsruhe reprocessing plant. Filters with particulate AC 6120 are used for sampling the air. The solutions are radiochemically treated according to their composition. The I-129 is measured either by X-ray spectrometry or by neutron activation. More than 99% of the calculated I-129 inventory, is released into the gaseous effluent during the dissolution process. The gaseous effluent scrubbers was measured. Since the beginning of 1975 measurements have been taken of the I-129 concentrations in a mixture of air from the solvent off-gas and the waste gas from both the dissolution vessel and highly radioactive waste solutions. The proportions of aerosol iodine and inorganic gaseous iodine contained in this mixture were determined. Residual iodine in the feed solution was analysed. After concentration of the highly radioactive waste solution, measurements were once again taken of the I content of the concentrate and of the waste gas from the concentrate vessel. During the course of 1975 every medium-active waste solution, both aqueous and organic, was analysed for I-129. The discharge of I-129 in low active liquid effluent was also checked over a period of almost two years. Solutions resulting from the purification by distillation of medium and low active aqueous waste and from the effluent from the final pond were also examined for I-129 over a period of two years. The results obtained are being used to draw up a complete record of the presence of iodine in the Karlsruhe reprocessing plant. (orig.)