The noncatalytic anhydride curing of an epoxy siloxane monomer, 1,3-bis[2-(3-{7-oxabicyclo[4.1.0]-heptyl}) ethyl]tetramethyldisiloxane, with 1,2,4-cyclohexane-tricarboxylic anhydride (H-TMAn) and methyl hexahydrophthalic anhydride (MeHHPA) was studied. Different H-TMAn concentrations, ranging from 1.3 to 58 mol %, were evaluated. The highest curing exotherm and highest glass-transition temperature were both found at 50 mol %. MeHHPA showed a sharp dependence of the thermal stability and thermal discoloration on the anhydride concentration. In contrast, the H-TMAn concentration did not much affect the thermal stability or thermal discoloration. H-TMAn could be diluted up to 3 times with MeHHPA to reduce the initial viscosity without a loss of noncatalytic reactivity. Unlike MeHHPA, H-TMAn experienced very little anhydride evaporation and weight reduction. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2301-2306, 2009