The concept of clandestine or illegal migration dates back to the 1930s but only
became prominent during the 1980s and 1990s. It is an umbrella term that refers to a
complex set of conditions and embraces various patterns. Instead of applying the conventional
but crude legal/illegal dichotomy this article suggests a fine-tuned analysis of clandestine
migration on a scale between the two poles. This contribution surveys the state of the art and
discusses various approaches in clandestine migration research; it aims at clarifying as yet
blurred definitions, discusses often problematical quantitative aspects, and gives an overview
of various major patterns in clandestine migration. Finally, in reflecting on the specific
conditions that determine clandestine migration, it argues that this phenomenon is a social
construct of the 21st century