Use your best judgment on who you decide to ask - there is no set formula for who should be your recommenders. We know it is not always possible to have a direct supervisor write your recommendation – we would not want you to jeopardize your current position for the application process. Look at the questions we are asking recommenders to complete. Find people who know you well enough to answer them. This can be a former supervisor, a colleague, someone you collaborate on an activity outside of work. How well a person knows you should take priority over level of seniority or HBS alumni status.