For the rapid and sensitive analysis of proteins, and to obtain reproducible results, an apparatus for isotachophoresis, Shimadzu IP-2A, was modified and the electrophoretic conditions were standardized. The apparatus was modified as follows; 1) Two peristaltic pumps were used instead of N₂ gas pressure system, for rinsing and refilling the capillary tube and the electrode chambers. 2) The flow lines were simplified into 3 lines, instead of 10 lines of the commercial apparatus. The electrophoretic conditions were changed as follows; 1) Hexane was overlayed on the electrolyte solutions to minimize the solubilization of CO₂, instead of the use of Ba(OH)₂. 2) The inner surface of the capillary tube was coated with hydroxypropyl methyl cellulose (HPMC), instead of using HPMC-containing leading electrolyte. The amount of the ampholyte mixture (Ampholine pH 3.5-10) to be applied was standardized to be 20μg. From these improvements and standardization, the interruption of electrophoresis by N₂ gas bubbles or by the precipitation of BaCO₃ were avoided and the procedure of isotachophoretic analysis was simplified. Serum proteins as low as 3μg could be separated into 20 UV-absorbing peaks within 16min of running time in good reproducibility.