To avoid adverse effects during the administration of [123I] meta-iodobenzylguanidine (MIBG), infusion of the drug that has been previously diluted is proposed. Stability of [123I] MIBG in sodium chloride solutions is studied, looking for incompatibilities in the formulation. Stability was tested on the basis of the percentage of free [123I] iodide on solid-phase extraction. No increase in percentages of free [123I] iodide was found in diluted and undiluted samples over time (P>0.05). Intravenous saline infusion of [123I] MIBG could be a useful tool for controlling the administration rate, minimizing the side effects and lowering the exposure of the staff to ionizing radiation.