The Strait of Istanbul links the Black Sea to the Sea of Marmara and is called the Bosporus. The Bosporus is one of the most dangerous waterways in the World, and has geopolitical, strategic and economic importance with approximately 50,000 transit vessels per year. Maritime casualties through this dangerous waterway are mainly due to fire or explosion, capsizing, collision or contact, foundering, sinking, grounding, and stranding. The reason for the casualties depends on many factors that can be grouped as: human errors (the pilotage), technical unavailability, lack of visibility sea and weather conditions, and ship traffic density. This paper investigates the maritime casualties in the year of 2004 with classifying the casualty forms: as ship type, local time of casualty and dominant factors of casualty. It is also aimed to compare the variation of casualty characteristics with using the data of past years.