Miniaturization of whole-column imaging capillary isoelectric focusing (CIEF) is discussed. A 1.2 cm capillary was used as a separation column for CIEF The experimental results for the analysis of two pl markers and the protein myoglobin showed that Waterloo, ON, Canada good CIEF separation results could be obtained. Secondly, a light-emitting diode (LED) was used as the fight source for the whole-column absorbance imaging detection. The focusing of both the p/ markers and myoglobin were observed with the LED light source. The whole-column imaging CIEF instrument was simplified and miniaturized by the use of the LED. Further developments are also discussed.