The report describes a preliminary application of supercritical fluid mass spectrometry (MS) techniques to the analysis of a middle distillate fuel, an emission particulate extract, and the emission particulates themselves. These techniques include capillary column supercritical fluid chromatography (SFC) (alone) and coupled with MS, direct fluid injection (DFI)/MS, and supercritical fluid extraction (SFE)/MS. These techniques are still in an early stage of development, but have demonstrated considerable potential for difficult analytical problems. The present work shows the feasibility of achieving high resolution separations of complex mixtures with SFC using nonpolar CO2 as the mobile phase. Additionally, these analyses have: provided an evaluation of the limitations of the present detector interfaces, resulted in further design improvements, and emphasized research areas for further investigation. The present work also shows that SFC/MS application to complex mixtures can provide good separations and usable mass spectra.