This book, which is published in the framework of the European Migration Network sponsored by the European Union, demarcates, describes and analyses at a first stage the phenomenon of illegal immigration in Greece. Illegal immigration coincided with the transformation of Greece from an immigration country to a receiver of immigrants and a permanent immigration destination in the early 1990s, as the overwhelming majority of immigrants who entered and stayed in Greece were illegal. Since then, the problem of illegal immigrants, namely third country nationals who do not fulfil the requirements for legal entry, presence or residence in the Greek territory, despite the consecutive regularisation programmes, is still on the agenda.

Even though the number of illegal immigrants has been drastically reduced, their total before the third regularisation of 2005 is estimated approximately to 300.000. The bulk of illegal immigrants, according to administrative statistical data, come from neighbouring (mainly Albania) and Eastern European countries, while the share of people from Asia (particularly Iraq, Pakistan and India) and Africa in the total number of newly arrived illegal immigrants has been increasing in recent years.

According to the Labour Force Survey data, relatively high percentages of unsecured, thus presumably illegal  immigrants are concentrated to those originating from Albania and the countries of the former USSR display. Such immigrants are (single) men, of relatively younger age and lower educational qualifications who suffer from unemployment and underemployment.
Illegal immigration is determined by the economic and social conditions that exist in the countries of origin, as well as the opportunities and terms of employment of illegal immigrants in Greece. In this context, the multiple employment and income opportunities that illegal immigrants obtain, especially in the extensive unofficial sector of economy, as well as the complex geographical setting, which renders the effective border control extremely difficult are considered as the main factors of illegal immigration.

Greece has attempted to manage illegal immigration through consecutive regularisation programmes, the stiffening of external borders-control, as well as the apprehension and expulsion of illegal immigrants. Also, it has already fully implemented the Schengen Agreement and has signed readmission agreements of illegal immigrants with various countries, along with bilateral agreements on the combat of illegal immigration with neighbouring countries. Nevertheless, it has not implemented a permanent and official system regarding the entry of legal immigrants.

The effects of illegal immigration should be distinguished into short- and long-term. As has been demonstrated in the book, the short-term effects of illegal immigration seem to be positive, since it provides flexible labour force in terms of employment and wage, which improves competitiveness. Nevertheless, the expected long-term benefits of illegal immigration are rather doubtful. Illegal immigration delays the restructuring of production, the substitution of labour with capital and new technology, which are the conditions for viable development. Illegal immigration is also possible to slow down the necessary changes in the inflexible legislative framework of labour market and influence the attitude of Greeks towards particular professions.