Electron mobilities were measured in ethane, ethylene, propane, cyclopropane, and propylene to complete the studies of the lower hydrocarbons. The effect of temperature on the mobilities in these liquids and in methane, n-butane, and xenon were also measured. Examples of the data are given in the order mobility (cm2/Vs), temperature (K), Arrhenius temperature coefficient (kcal/mol): methane, 430, 140, −0.16; ethane, 0.97, 200, ∼3; ethylene, 0.0030, 170, —; propane, 0.55, 238, ∼3; n-butane, 0.073, 250, ∼4; cyclopropane, 0.0043, 234, ∼4; propylene, 0.008, 234, ∼4; xenon, ∼1200 at 40 V/cm, 198, 0. The mobilities in the C2–C4 hydrocarbons are independent of applied electric field strength E up to 20 kV/cm; that in methane is independent of E up to 2 kV/cm; that in xenon decreases as E−1/2 between 33 and 300 V/cm and decreases slightly more rapidly at higher field strengths. The density-normalized ranges of the secondary electrons in each of the liquids is independent of temperature. The correlation between the ranges of the secondary electrons and the mobilities of thermal electrons observed in other liquids (ref. 2) persists for the simple hydrocarbons.