The ever - increasing expansion of relations and human contacts in different fields, especially in economy, has caused that monetary and banking dealings also proportionally increase and develop. The emphasis of Islamic jurisprudence on the unlawfulness of usurious transactions among the followers of Islam and it's undisputed reasons has raised this question for many people as to the range of the domain of this prohibition the kinds of transactions and economic relations they can maintain.This paper tries to introduce a way for the researchers at the country's economic and banking field in which cases they can enter usurious transactions, and where they cannot. At the beginning of this paper the writer has tried to explicate the relevant terms in jurisprudence, law and economy.