[en] The preparation of sup(99m)Tc radiopharmaceuticals using the electrolytic reduction of sup(99m)Tc pertechnetate was investigated. The effect of current intensity, amount of current, pH and applied voltage on the reduction of the Tc-VII and its incorporation into the radiopharmaceuticals was evaluated. The results indicate that the electrolytic method gives high and reproducible labelling yields and compounds with good radiochemical purity. Procedures for the preparation and control of the following sup(99m)Tc radiopharmaceuticals were standardized by the authors: Tc-tin colloid, Tc-red blood cells, Tc-HSA, Tc-albumin microspheres, Tc-EHDP, Tc-gluconate and Tc-glucoheptonate. A portable electrolytic labelling instrument was designed for use in hospitals