The rescue excavations undertaken on the European and Asian sides of Istanbul in recent years have revealed significant information regarding Byzantion, which had an active and strategic role in Hellenistic trade. A highly important part of the work in question was undoubtedly the excavations carried out within the scope of the Marmaray Project. A large number of artefacts and structures were brought to light throughout the excavations of the project at the Sirkeci station. Among these finds were amphora stamps which had previously been little known. The excavations uncovered finds that shed new light on the commercial relations between Byzantion and two important cities in the Black Sea region - Chersonesus and Sinope. This study results from documenting these amphora stamps. Although these amphora stamps provide information regarding a limited geographical area within Byzantion, nevertheless, they provide some idea regarding the larger commercial relationships of the city.