Modern (high-pressure) liquid chromatography (LC) is uniquely suited to the trace analysis of a wide variety of non-volatile or labile materials, both organic and inorganic in composition. In addition to the gentle conditions of separation in LC, accurate analyses can be made as a result of the high resolution afforded by the unique interactions in liquid systems with the four LC methods liquid-solid, liquid-liquid, ion exchange and exclusion. Sensitive LC detectors are now available which also permit highly selective measurements, some of them not obtainable by other chromatographic techniques. The sensitivity and accuracy of trace LC analyses are affected by the chromatographic sampling technique, calibration procedure, sample pretreatment and column resolution. For instance, experiments show that the sensitivity of methods based on both peak height and peak area measurements is influenced by the efficiency of the column, the velocity of the mobile phase, and the value of the capacity factor(k′) for the solute. Detection sensitivity can also be influenced by the type of pumping system used in the LC apparatus. Based on these considerations, preferred conditions for the analysis of trace components by LC can now be established.