Silver nanoparticles loaded on NH4+-type zeolite, AgNPs-NH(4)ZSM5, was developed as an inorganic matrix for laser desorption/ionization mass spectrometry of low molecular weight compounds. It was found that AgNPs-NH(4)ZSM5 could work as an efficient Ag+ donor to ionize analytes and that zeolite worked as a heat bath to prevent the destruction of AgNPs after the photoexcitation. The AgNPs-NH(4)ZSM5 was applied to laser desorption/ionization mass spectrometry of biologically active substances with low molecular weights including acetylsalicylic acid, L-histidine, glucose, urea, cholesterol, and those in human serum. (C) 2013 Elsevier B.V. All rights reserved.