Al-cBN cermets have been hot pressed at temperature between 800oC and 1100oC and pressure of 50MPa in vacuum. The effect of particle size of the starting powders as well as the effect of starting compositions and temperature was investigated. The materials could only densify up to 84-92% of theoretical density. After hot pressing at 800oC only Al and cBN could be observed by XRD, whereas higher hot pressing temperature result in the formation of AlN and AlB2 which retard the densification. The microstructure of the hot pressed material was studied using scanning electron microscopy. It was observed that oxide layers exist at the interface between Al and cBN phases. The presence of these oxide layers resulted in blocking the Al from spreading and therefore preventing full densification.