Abstract: A composite adhesive featuring a matrix phase that includes a cyanate ester and a filler or reinforcement phase that includes a plurality of bodies of at least one material comprising a high shear strength and/or high modulus material. Preferably, the filler also possesses at least one of high thermal conductivity and low coefficient of thermal expansion. Unlike certain commercially available cyanate esters, those of the instant invention substantially maintain or even increase in strength upon addition of the filler to the system. The instant composite adhesives may also display reduced coefficients of moisture expansion relative to the unfilled or “neat” resin. Such a composite adhesive is extremely useful for joining articles where high strength and minimal swelling in moist environments are required, such as in the precision equipment industry.