We discuss a few aspects of star formation triggered by H II regions. We show that, in a given region, different processes can be at work to trigger star formation in the layer of neutral material collected around the ionized gas, during the expansion of the H II region; stars of all masses can be formed there. We show that the collect & collapse process can trigger the formation of massive stars, even in an inhomogeneous (an possibly turbulent) medium. The luminosity of the most massive second-generation star observed until now to be formed by triggering corresponds to an O8 star.