  We calculate the formation rates of low-mass X-ray binaries with a black
hole. Both a semi-analytic and a more detailed model predict formation rates
two orders of magnitude lower than derived from the observations. Solution of
this conundrum requires either that stars with masses less than 20M$_\odot$ can
evolve into a black hole, or that stellar wind from a member of a binary is
accompanied by a much larger loss of angular momentum than hitherto assumed.
