This study focuses on marine accident data regarding accidents that occurred between the years 1998-2010 for ships within the oil tanker category. Data in the study include accident reports, which are recorded in the Global Integrated Shipping Information System (GISIS) and country reports. Textual accident data in the GISIS database were tabulated, thus creating a systematic database. By using accident data from this database, a marine accidents map for oil tankers was developed via the ArcGIS 10 program, the areas with the highest accident incident rates were determined, and reasons for oil tanker accidents were revealed through the assessment of factors such as accident type, accident incident number, accident scope, ship tonnage, navigational sea area type, and accident's impacts on the environment, economy and personnel. The study showed that very high risk areas for oil tanker marine accidents include the Singapore Strait and Oresund, and high risk areas are the Bristol Channel, Suez Channel, Strait of Hormuz, Great Belt, Piraeus, Hull, Istanbul Strait, and Amsterdam, respectively. The study also established that oil tanker accidents are related to ship tonnage and navigational sea area type.