Streams containing I-125 coming from radioimmune analysis (RIA) classified as low-medium activity radioactive waste are generated by different treatments applied in "in vitro" techniques. The consequence is an accumulation of solutions containing I-125 whose storage at sanitary centers poses an important problem. On the basis of the specific activity of the wastes and the dumping authorization of the facility, there are three possible ways of handling: direct discharge, discharge after temporal storage during which the activity of the solution decays, and the management by the authorized company (ENRESA). When the third way is applied, membrane treatment should be considered. Using membranes, important reduction coefficients in volume, about 10:1, can be achieved. The aim of this work is the declassification of I-125 solutions as a radioactive liquid waste using membrane techniques.