Boilover is defined as a violent ejection of fuel due to the vaporization of a water sub-layer, resulting in an enormous fire enlargement and formation of fireball and ground fire. This paper focuses on the physical principles behind the thin-layer boilover phenomenon, and on the improvement of the thin-layer boilover modeling. Small scale field and laboratory experiments, with a mixture of diesel and oil, and reservoirs ranging from 0.08 to 0.3 m, have been performed. High-speed visualizations and image processing, in parallel to temperature and mass loss measurements allows to better understand the water boiling, and the consequent flame enlargement. The modeling of the boilover period is done through the calculation of the pre-boilover burnt mass ratio and the boilover intensity based on the mass loss and on the flame enlargement. (C) 2013 Elsevier Ltd. All rights reserved.