The theoretical potential of open tubular columns in terms of resolving power, speed of analysis, peak capacity, and sample capacity are given, The requirement and constraints of chromatographic equipment such as hydraulic pump, injector, connector tubing, detector, etc., in conjunction with an open tubular column, are examined. Speed of analysis, peak capacity, and sample capacity for packed and open tubular columns are also compared. Open tubular columns of i.d. ≤7.5 μm achieved resolving power that is equal to or better than conventional, state-of-the-art 5-μm particle-packed columns (h = 2, ν = 5), for a given analysis time. The use of microbore open tubular fused silica columns, for both the separation column and detector flow cell for on-column detection, is demonstrated.