Investigation of the interaction of hydrogen with alkaline earth manganites (IV) AMnO(3) (A = Ca, Sr, Ba), dispersed with 1 at.% Pt, has revealed an unprecedented uptake of hydrogen by BaMnO3/Pt to the extent of similar to 1.25 mass% at moderate temperatures (190-260 degreesC) and ambient pressure. Gravimetric sorption isotherms and mass spectrometric analysis of the desorption products indicate that approximately three hydrogen atoms per mol of BaMnO3/Pt is inserted reversibly. The nature of hydrogen in the insertion product, BaMnO3H3, is discussed. The work suggests the possibility of developing new hydrogen storage materials based on electropositive metal-transition metal-oxide systems. (C) 2004 Elsevier Ltd. All rights reserved.