Black holes in binaries

Recent observational successes are providing a new impetus to the study of binaries containing stellar-mass black holes.  I will start with a very brief review of the current understanding of massive binary evolution leading to the formation of black-hole binaries.  I will then focus on a few of the outstanding issues in interpreting both X-ray and gravitational-wave observations and propose pathways for improving our understanding of some challenging aspects of binary evolution.