Many researchers have investigated the smuggling phenomenon with different viewpoints. Some of them, refer to it as a crime and try to analyze its criminal and judicial aspects in their papers. Others, regard smuggling as only an economical problem and also there is a third group which tries to find the causal issues in smuggling and realizing its consequences. In this article, it is attempted, to discuss the theories of smuggling, its types, etc first. Afterwards, different viewpoints which can be classified in three groups (legal- penal, empirical, causal) will be investigated. We are also about to find other contributory factors which have not been recognized so well.