Radioimmunotherapy has become a highly promising oncologic therapeutic modality with established clinical efficacy in the last decades. Monoclonal antibody rituximab was labelled with 131I used in the treatment of B cell non Hodgkin's Lymphoma (NHL). In this study, rituximab, a monoclonal antibody was labelled with 131I using chloramin T and iodogen method to prepare radioimmunoconjugated 1311-rituximab with twospecific activities. The optimized conditions of radioiodination of rituximab were carried out. The optimized chloramin T concentration for the oxidation of 740 MBq of Na131I solution and 3000ug of Rituximab was 100 ug. Reaction time was 5 minutes at room temperature. The labeling reaction has stopped using sodiummetabisulphite. lodogen coated tubes which were used in the labelled 3000 ug antibody and 740 MBq is 80 ug. Labelling efficacy was controlled by TLC. The reaction mixtures were purified through the sephadex G-25 PD10 pharmacia column. The collected 131I-Rituximab was filtered through a 0.20um milipore sterile filter. The labeling yields was more than 95 percent of ch T and 85 percent of iodogen methods. Radiochemical purity of the radiopharmaceutical after purification was more than 99 percent. The product has been passed the test for sterility, bacterial endotoxins, to be sufficiency invitro stable after labelling, 131I-Rituximab is ready for clinical use.