There are many hard materials that are considered to be candidates for structural applications under extreme conditions such as very high temperatures. But, one of the common characteristics for these hard materials is their brittleness at ambient temperatures. Many of them need very high temperatures for plastic flow. So, even, fundamentals for plasticity such as operating slip systems and their CRSS values have yet to be known for many of them. However, there is a chance for these hard materials to plastically deform in the form of micropillars of the micron-meter size even at ambient temperature, from which we can obtain the information of operating slip systems and their CRSS values. The results obtained for some brittle transition-metal silicides of the M5Si3-type such as Mo5Si3, Nb5Si3 and Mo5SiB2 and those of the MSi2-type such as MoSi2, VSi2, CrSi2, NbSi2 and TaSi2 will be presented.