A considerable part of world merchandise is transported by sea, and with about 150,000 crew members working on the ship types of interest for this thesis there is much at stake if an accident occurs, both with respect to human lives and financial losses. Since fires have previously shown to be responsible for many accidents with severe consequences, the aim of this thesis has been to investigate the risks of fires and/or explosions in the machinery space of oil tankers and container vessels. By performing a casualty database search and reviewing previous studies in this area, as well as developing a risk model to evaluate the different possible fire scenarios, it is concluded that electrical failures and fuel leaks are responsible for most fire accidents, with generators, pumps and boilers being the most critical components. The expected frequency of a fire and/or explosion accident, calculated for the fleet of interest, amounts to 2.5 ×10−3 incidents per shipyear, resulting in the loss of 0.0003 lives per shipyear. Furthermore financial losses of about 12,000 USD per shipyear can be expected. Though there are some limitations in the methods used, due to incomplete statistical data and difficulties in drawing general conclusions since every vessel is unique in its design and construction, it is clear that considerable benefits may be obtained by a more detailed costbenefit analysis for a vessel with respect to fires and explosions.