A method for assessing the societal risk of transporting liquefied petroleum gas (LPG) and liquefied natural gas (LNG) is described, and is illustrated by application to the transport of LPG by tank truck and LNG by tanker ship in the U.S. Data on past experience and projected future handling of these liquefied gases are used with analysis of flammable plume formation and ignition, and population distributions, to estimate the risks of fatalities from tank truck and tanker ship accidents. From an estimated 52 significant accidents per year with LPG tank trucks at the present truck-associated transportation rate of 20 billion gallons of LPG per year, a fatality rate of 1.2 per year is calculated. For the projected 1980 importation of 33 billion gallons by tanker ship, a fatality rate of 0.4 per year is calculated, using a conservatively high one chance in 20,000 of a significant accident per trip. Comparison with fires and explosions from all causes in the U.S. and Canada leading to 10 or more fatalities shows that these are 100 times more frequent than the predicted frequency of comparable LPG and LNG accidents. Tabulations of experience with spills of flammable volatile liquids are included.