The imminent return of more than 35,000 Burundians from Tanzania poses major logistical challenges to aid agencies and the densely populated country they fled amid civil war almost 20 years ago. The return could degenerate into a 'humanitarian disaster' if they ignore a 31 December deadline to leave willingly and end up being deported en masse. While Burundi has absorbed more than half a million refugees since 2002, never before has it had to contend with such a large number of returnees in such a short space of time.