Closed vessel and vented ethylene/air explosion tests were carried out in a 26 1 spherical chamber. The confined explosions were conducted with three initial turbulence levels (including quiescent conditions) and initial pressures of 1, 1.5 and 2 bar(a). The vented experiments were conducted with the same three initial turbulence levels, initial pressures of 1, 2 and 3 bar(a), one vent ratio and two nominal ratios of vent opening pressure to initial pressure. The data were used to correlate a semi-empirical model for confined and vented gaseous explosions, The experiments enabled determination of the impact on explosion pressure development of burning velocity enhancement due to initial turbulence, cellular flame formation and venting-induced turbulence. Reasonable agreement was obtained between measured and predicted explosion pressures for both confined and vented explosions. The relationships between explosion pressure and rate of pressure rise. and various experimental parameters such as initial pressure and initial turbulence, followed generally accepted trends.