Field-ionization relative sensitivities were determined for 18 n-alkanes and 22 cycloalkanes in the presence of acetone at 270 to 300°C. The relative gram sensitivities for n-alkane and n-alkylated cyclohexanes, decalins, and perhydroanthracenes/perhydrophenanthrenes decrease linearily with decreasing reciprocals of their molecular weights. Since the first three correlations result in negative changes in the relative mole sensitivities for these three families with increasing carbon number, alteration in their acetone perturbed ionization necessarily occurs between about C25 and C32. Linear correlations exist between the mole sensitivities for parent cycloalkanes containing either six-membered or six- and five-membered rings relative to cyclohexane and -Z(H;H). The slope of the former correlation is considerably larger than the latter one. These results and a set of assumptions generated the sensitivities required for quantitative analysis of the field-ionization mass spectra (FI/MS) of the 200 to 325, 325 to 425, and >425°C saturates from a hydrotreated shale oil. The agreement in the analytical results obtained by FI/MS, 70-eV electron impact mass spectra (EI/MS) (ASTM Method for Hydrocarbon Types Analysis of Gas-Oil Saturate Fractions by High Ionizing Voltage Mass Spectrometry [D 2786]), and flame-ionization detection gas chromatography (FID/GC) ranges from excellent for the 200 to 325°C saturates to nonexistent for the >425°C fraction. Thus, all three methods require additional developmental research in an attempt to obviate deficiencies and, hence, delineate their ultimate applicability.