The fast "fluidic logic" injection system developed by Gaspar and co-workers for use in high-speed capillary gas chromatography (GC) was evaluated at pressures between 4 and 25 bar. When correctly controlled, the fluidic device performed well. A sample band width of 5 msec was normally obtained, for all compounds injected. The fluidic logic injector enabled precise H versus u studies on two 8 m × 50 µm I.D. capillary GC columns, coated with cross-linked OV-1, to be made. For n-pentane, which was not retarded, a maximum of 400,000 plates were obtained, at a column inlet pressure of 20.0 bar. About 180,000 plates were obtained for n-dodecane, having a capacity ratio of 4. The observed plate height curves were compared with the Golay—Giddings plate height model. Good agreement between the measured and theoretical plate numbers was found, even for the unretained compound, thus demonstrating the abscence of dead volumes in the fluidic injector design.