Zirconium diboride-silicon carbide ceramics with relative densities in excess of 95% were produced by reactive hot pressing (RHP) at temperatures as low as 1650 degrees C. The ZrB2 matrix was formed by reacting elemental zirconium and boron. Attrition milling of the starting powders produced nanosized (< 100 nm) Zr particulates that reacted with B below 600 degrees C. The reaction resulted in the formation of nanoscale ZrB2 crystallites that could be densified more than 250 degrees C below the temperatures required for conventional ZrB2 powder. Because of the low-temperature densification, the resulting ZrB2 grain sizes were as small as 0.5 +/- 0.30 mu m for specimens densified at 1650 degrees C and 1.5 +/- 1.2 mu m for specimens densified at 1800 degrees C. Vickers hardness, elastic modulus, and flexure strength of fully dense materials produced by RHP were 27, 510, and 800 MPa, respectively.