A radioimmunoconjugate of biotin conjugated with the bifunctional, macrocyclic chelating agent tetra-azacyclododecanetetra-acetic acid (DOTA) and labeled with indium 111 (In-111). Biotin is a water-soluble B-complex vitamin, present in minute amounts in every living cell, while its level in cancerous tissue is higher than that of normal tissue. In 111-DOTA-Biotin could be used in 3-step pre-targeting radioimmunotherapy that employs tumor targeting antibody conjugated with streptavidin, the natural ligand of biotin. Check foractive clinical trials using this agent.