For the past decade and a half a new alloying strategy that involves the combination of multiple principal elements in high concentrations to create new materials called high-entropy alloys has been emerging. High-entropy alloys have greatly expanded the compositional space for alloy design. The multidimensional compositional space that can be tackled with this approach is practically limitless, and only very small compositional regions have been investigated so far. Nevertheless, a few high-entropy alloys have already been shown to possess good mechanical, magnetic and invar properties, exceeding in part those of some conventional alloys, and more such high-entropy alloys are likely to be discovered in the future.