A regional updating technique is suggested for the global ionospheric delay model (Klobuchar's <1987> model). The updating procedure uses series of values of the ionospheric delay (ID) which are reconstructed from distance measurements at two Global Positioning System working frequencies. We consider the situation where Klobuchar's model is updated from measurements from a single ground-based reference station. We exemplify the use of a regional updating of the ID model under undisturbed ionospheric conditions, as well as under solar eclipse and magnetic storm conditions. In all cases presented, using the proposed technique the standard deviation between predicted and measured ID values was reduced by a factor of 1.2--2.8 as compared with Klobuchar's original model used under the same conditions. A tentative estimate is made of the variation in the ionospheric rms error in determining the user's location (UPL) through the use of the regional updating technique. For the examples considered in this study, on applying the regional updating of Klobuchar's model, the ionospheric rms error in determining the UPL was found to be lower by a factor of 1.3--2.6 than that obtained by using the same model without updating. ¿ 2000 American Geophysical Union