We analyzed three vacuum gas oil distillation fractions, 295-319 degrees C, 319-456 degrees C, and 456-543 degrees C, with a home-built external electron ionization (EI) 7 T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. EI at 10 eV allows soft ionization of aromatic compounds in the vacuum gas oil range. Unambiguous elemental composition assignment provides insight into compositional variations at the molecular level; for example, ultrahigh resolving power (m/Delta m(50%) approximate to 300 000 at ink 300) and mass accuracy (< 0.4 ppm) readily resolve C-3/SH4 doublets (3.4 mDa mass difference) across the full m/z range of interest. To our knowledge. this is the first time that hydrocarbons and sulfur-containing hydrocarbons have been completely mass-resolved across the full VGO range. Aromatic hydrocarbons are the major detected components in all three samples. In addition, many sulfur-, nitrogen-, and oxygen-containing compounds were directly observed. The concentrations of the heteroatomic species increase with boiling point. Detailed data analysis revealed compound types (rings plus double bonds) and their carbon number distributions for hydrocarbon and heteroatomic compounds in the distillation fractions and increasing average molecular weight (or carbon number distribution) and aromaticity with increasing boiling temperature of the petroleum fractions. The present analysis requires only micrograms of sample, is fast (single time-domain data set acquired in a few seconds), and highly reproducible.