Bispecific immunoconjugates that bind a target tumor antigen and a small molecule, carrying the active payload, are used to develop pretargeting strategies combining the advantage of antibodies, to track tumor cells in vivo, and of small radiolabeled molecules, that clear rapidly from normal organs and minimize toxicity. Pretargeting approaches using the biotin/avidin recognition system and those using bispecific anti-tumor x anti-hapten antibodies have been tested in the clinic for both immunoscintigraphy and radioimmunotherapy, with very encouraging results. Thus pretargeting approaches remain a viable strategy to develop active cancer treatments against hematological malignancies and solid tumors.