A major fraction of today's analytical separation problems cannot be solved using gas chromatography (GC) or high performance liquid chromatography (HPLC). However, many of these problems can be solved using capillary supercritical fluid chromatography (SFC). This is true because the combination of low-temperature, solvating mobile phase; high-efficiency separation; and sensitive universal detection is possible today only by combining capillary SFC with a flame ionization detector. Many solutes with molecular weights too high (or volatilities too poor) for GC, or those without thermal stability, can be separated by SFC under mild conditions. Also, there are no special solute requirements for sensitive detection with the FID, as is the case with sensitive HPLC detectors. While these features represent the major new capabilities offered by SFC, the role of selective detectors is still just as important in SFC as in any other form of chromatography.