The effect of the gel composition, electric field strength, and capillary length on the separation of DNA sequencing reaction product was investigated in order to achieve high-speed DNA sequencing on a large-scale for the Human Genome Project. In this study, we prepared gel-filled capillaries differing in gel concentration (3% T similar to 6% T), degree of crosslinking (0% C similar to 5% C), and capillary length (15.3 cm similar to 36.3 cm). Fluorescence-labeled A-termination sequencing reaction product (M13mp18 template) was first separated by capillary electrophoresis using the gel-filled capillaries prepared here in electric fields from 200 V/cm to 414 V/cm and then detected at 560 nm by using an on-line argon ion laser (488 nm)-induced fluorescence detector. In conclusion, the use of the short capillary, high concentration gel, and high electric field realizes high-speed separation of DNA sequencing reaction product with high resolution. Under optimum separation conditions, only 10 min is required for sequencing of 250-base DNA.