  The stellar initial mass function (IMF) determines the relative number of
stars born at a given mass. Despite the tremendous effort to establish a
universal IMF, the astronomical literature offers a wealth of diverse evidence
for IMF variations. This review was prepared for a controversial debate at the
conference ``Starbursts -- Near and Far'' at Ringberg Castle, 2000, and gives a
one-sided portrayal in favour of IMF variations. I will summarise the empirical
evidence that the IMF varies with time, with environment, and for all stellar
masses. While I see no obvious systematic trend in most regions of our Galaxy,
there is at least an indication that the IMF is biased towards more massive
stars in the early universe and in starbursts.
