A literature survey is presented on the effect of pressure on soot formation in flames For continuous flames the main effect is an increase in soot formed proportional to pnwhere 1 < n < 3. However the reverse is true for gaseous explosions, as the soot yield decreases with pressure, presumably because the combustion products have a greater chance to approach equilibrium. Diffusion flames show a low pressure limit below which soot does not occur, while for premixed flames the critical fuel/air ratio for soot formation is found to be essentially independent of pressure, although the proportion of tarry materials may vary.