For months now Europeans have been witnessing chaotic scenes of migrants pouring into Greece, Italy and Central Europe.
The EU is playing catch-up, struggling to co-ordinate asylum policy between 28 member states.
But it is a sensitive issue, affecting sovereignty and national relations with diaspora communities, such as Afghans in the UK, or Algerians in France.
The UK and Ireland opted out of most EU asylum policy, sticking to their own rules.
The focus now is on a mechanism to distribute new asylum seekers across the EU - but countries are arguing over that.
Many will qualify as refugees - especially those who fled Syria, Afghanistan or other conflict areas. A refugee is someone fleeing war or persecution, with a right to international protection.
But how many failed asylum seekers are sent back by EU countries? Is there any EU-wide pattern on asylum?
Identity checks
In 2015 the largest migrant groups in Europe by nationality are Syrians, followed by Afghans, then migrants from Eritrea, Nigeria and Somalia.
War and human rights abuses have plagued all those countries, so many of those asylum seekers count as refugees.
But each case is different - some will find it harder than others to prove their refugee credentials.
Many lack passports or other ID, having risked their lives in the Mediterranean and Balkans, abused and exploited by criminal gangs.
Establishing nationality can be a long process - and those decisions can be disputed by countries asked to take migrants back.
Many migrants reaching the EU from sub-Saharan Africa or the western Balkans fail to get asylum, as they are classed as economic migrants.
One of the incentives for irregular migrants is the fact that fewer than half of failed asylum seekers are actually expelled.
In 2013 the EU sent back just 39% of those refused asylum, the EU Commission says in its European Agenda on Migration.
Another stumbling block is that agreements with non-EU countries on asylum returns are quite patchy.
Many readmission agreements have been negotiated, for example with Pakistan and Bangladesh. But the EU has no such deal with China or Algeria.
And the Cotonou Agreement, obliging sub-Saharan African countries to take back failed asylum seekers, has not stopped a huge exodus of economic migrants from there. The Commission admits that the EU must offer more aid, to facilitate more migrant returns to Africa.
There are also plans to widen the mandate of Frontex, the EU border agency, so that it can help send migrants back.
