Manganese(II) is employed as a contrast agent with magnetic resonance imaging (MRI) for study of neuronal activation in rats and mice. However, at the concentrations required for MRI, Mn may induce pharmacological or toxic effects. Positron emission tomography (PET) imaging of (52)MnCl2 at tracer doses has the potential to allow similar Mn studies as manganese-enhanced MRI while providing quantitative results and avoiding toxic effects. In this work, (52)MnCl2 is produced and characterized as a PET tracer in phantoms and in rats.