Zirconium diboride (ZrB2) ceramics were prepared by reactive hot pressing of ZrB+B powder mixture. Formation of a transient liquid due to eutectic reaction of ZrB2+Zr -> Leu(ZrB2+Zr) at 1661 degrees C following peritectic decomposition of 2ZrB=ZrB2+Zr at 1250 degrees C during heating up of the ZrB+B mixture facilitated densification. The liquid phase was subsequently eliminated via reaction of B with Zr in the eutectic liquid Leu(ZrB2+Zr) to result in a dense ZrB2 ceramic. Full density was reached after reactive hot pressing at 1900 degrees C under 30 MPa for 1 h. The ZrB2 ceramic had a refined microstructure consisting of grains of <1.5 mu m in size and relatively good Vickers hardness (21 +/- 2 GPa) and flexural strength (595 +/- 63 MPa).