Bismaleimide-triazine (BT) resin/hexagonal boron nitride (h-BN) composites are prepared, and the effects of h-BN content on the thermal and dielectric properties are studied in the view of structureproperty relationship. It is found that the introduction of the BN in the BT resin dramatically improve the thermal conductivity of BT resin. The thermal conductivity of the composites is up to 1.11 W/m.K, with an h-BN concentration of 50 wt %, which is increased bysix times compared with the pure BT resin. The BT resin/h-BN composites also exhibit excellent thermal properties, with the glass transition temperatures above 200 degrees C, and thermal decomposition temperatures over 390 degrees C. Moreover, the composites possess good dielectric properties. Their dielectric constant and loss tangent (tan ) are less than 4.5 and 0.015, respectively. The results indicate that the BT resin/h-BN composites are promising as efficient heat-releasing materials in the high-density electronic packaging technology. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013