Manganese(III,IV) oxide minerals are known to strongly adsorb lead and have been proposed as amendments to lead contaminated soils. Manganese release in response to lead sorption has been described in previous studies, however, the form was not characterized. The objective of this study was to characterize the oxidation state of manganese released during lead sorption on birnessite, a mixed oxidation state manganese mineral. Birnessite was synthesized (average oxidation state of 3.47) and was used to sorb lead using the stirred-flow reactor method. Flow cell reactions were performed by addition 2mmol per L lead perchlorate solution at pH 3 at a flow rate of 3mL per min into a reaction cell with 60mL of birnessite suspension. Three mL fractions were collected at one minute intervals into tubes containing pyrophosphate as a Mn(III)-stabilizing ligand. The Mn(III)-pyrophosphate complex concentration was measured by UV-Vis absorbance at 258nm. Total manganese and lead in filtrates and reductively dissolved lead-sorbed birnessite were measured by atomic absorption. Mn(III) release was observed after 10 minutes and accompanied lead sorption. The presence of Mn(III) was confirmed by reduction with sulfuric acid and oxalate. Lead breakthrough did not occur until 40 minutes after initial introduction began. Sorption induced release of Mn(III) could play an important role in soil redox processes, such as organic matter oxidation and nitrogen cycling.