Recently researchers from universities, industry and governmental laboratories completed a collaborative study that investigated the impact of different types of organic fuel additives on soot and PAH emissions from military gas turbine engines. The main objective of this program was to obtain fundamental understanding of how even a small changes in fuel composition can affect soot and PAH emissions. Six different combustors namely, a premixed flame, a co-flow diffusion flame, an opposed-flow diffusion flame, a well-stirred reactor, a shock tube, and a swirl-stablized combustor were used to investigate the impact of additives covering a wide range of combustion conditions. The experimental results from this study were then modeled using variety modeling packages and mechanisms. This paper will summarize the key results from studies of the effects of phosphorus additives, trimethyl phosphite, trimethyl phosphate, diethyl allyl phosphate, and dimethyl methyl phosphonate on soot and PAH for several gaseous fuels and a simple JP8 surrogate, heptane/toluene.