A review is presented of fire studies beginning with the work of Ingberg at the National Bureau of Standards, who attempted to relate the severity of a fire endurance test in the laboratory to the conditions existing during actual building fires. He showed the importance of weight of combustibles per unit floor area as a major factor. He recognized the importance of ventilation in controlling fire behavior but did not specify it as a separate variable. Fujita in Japan is credited with emphasizing the importance of ventilation. His work has been followed and enlarged by others around the world. Ventilation parameters, compartment geometry, and fuel arrangement have been shown to exert a powerful influence. The radiance from a burning building is dependent to a large extent on the nature of the ventilating openings. Fire severity is not well defined, since it depends on the interaction of the temperature-time curve developed during a fire and the thermophysical properties of the materials exposed. There is a great need for further research on the influence of fuel arrangement, building geometry, and ventilation on fires in buildings.