Application of open tubular capillary columns in LC is demonstrated. Several types of capillary columns, physically coated, chemically bonded, soil phase, and ion exchange, were prepared and their performance were evaluated with instruments specifically developed for capillary LC. A UV spectrometer which had the cell volume of 0.03–0.1 μl was used as the detector, and a gas-tight syringe set on a micro feeder was used as the pump. Glass capillary columns of the dimensions 30–60 μm i.d. × 3–20 m were generally employed, and typical mobile phase flow rates of 1–2 μl/min were used.