The effects of a wide variety of polar compounds and fuel additives on both the electrical conductivity and electrostatic charging tendency of both silica gel treated n-heptane and Jet A fuels have been examined. Conductivity was determined by ASTM D3114 and charging tendency by measuring the current developed as the hydrocarbon liquid passed through an electrically isolated filter holder containing a paper, fiberglass or teflon screen filter. Of all the compounds and additives tested, water came closest to fulfilling the definition of an ideal pro-static agent, viz, a compound that greatly increases the charging tendency of a fuel without increasing its conductivity. After saturation with water, the charge density of clay-treated Jet A fuel increased by a factor of 23 and that of an untreated Jet A by a factor of 7. The conductivities of both fuels remained essentially the same. Since water did not increase the charging tendency or conductivity of silica gel-treated n-heptane it was concluded that it is not water per se, but rather its interaction with some constituent in the jet fuel that is responsible for its pro-static effect.