Ships trade internationally and have to call at various ports all over the world. many ships may not call at any of their home ports for a considerable period and it is possible that during a certain period of time Ship's Certificates may not have been renewed or maintenance in general has suffered due to various reasons. Therefore, it is imperative that ships must be inspected at various ports to ensure compliance with rule requirements as regards safety, maintenance, manning, etc. This control is termed as Port State Control.

Port State Control (PSC) is the inspection of foreign ships in national ports to verify that the condition of the ship and its equipment comply with the requirements of international regulations and that the ship is manned and operated in compliance with these rules.