This report describes the current status of knowledge on flame and pressure development in turbulent gas explosions. Special emphasis is given to gas explosions occurring in obstacle environments. The problem is discussed in relation to experimental results obtained in both large-scale and small-scale situations, as well as results from theoretical studies. Special attention is given to the influence of confinement, obstacle shape and distribution, mode of propagation (axial, radial and spherical), fuel - air mixture and scaling characteristics.