  We study the evolution and fate of solar composition supermassive stars in
the mass range 60 - 1000 Msun. Our study is relevant both for very massive
objects observed in young stellar complexes as well as supermassive stars that
may potentially form through runaway stellar collisions. We predict the
outcomes of stellar evolution employing a mass-loss prescription that is
consistent with the observed Hertzsprung-Russell Diagram location of the most
massive stars. We compute a series of stellar models with an appropriately
modified version of the Eggleton evolutionary code. We find that super-massive
stars with initial masses up to 1000 Msun end their lives as objects less
massive than ~150 Msun. These objects are expected to collapse into black holes
(with M < 70 Msun) or explode as pair-instability supernovae. We argue that if
ultraluminous X-ray sources (ULXs) contain intermediate-mass black holes, these
are unlikely to be the result of runaway stellar collisions in the cores of
young clusters.
