The formation of high mass stars

I review current controversies and uncertainties surrounding the formation of massive stars in conventional star forming regions. In contrast to the situation for low mass stars, massive star formation is currently not well understood, a difference that may be readily traced to the importance of a variety of feedback processes in the case of massive stars. I shall show that, notwithstanding considerable progress in numerical simulations over the last decade, there are still many shortcomings in such simulations, owing to the difficulty of resolving and following the impact of feedback on a range of spatial scales. Currently, therefore, there is not even any consensus as to whether massive star formation is just a scaled up version of low mass star formation or whether different mechanisms are required. Meanwhile, observations are clarifying a number of necessary properties for successful models. Here we discuss evidence that the star formation process yields a maximum stellar mass, as well as recent data on circumstellar discs around OB stars