Total electron densities in the magnetospheric trough are used to develop an empirical model of this region. Average trough filling from early morning through to afternoon local times is found to be 0.56¿0.08 cm-3h-1. Growing trough densities are found to change to falling trough densities at a magnetic local time (&PHgr;TP) related to Kp, i.e., &PHgr;TP=0.145 Kp2-2.63 Kp+21.86. Trough densities are found to fall in the late afternoon and through evening local times with an average rate of -0.83¿0.15 cm-3h-1. The derived model is smooth and continuous throughout all local times and may be used in a simulation or for defining a static description of typical total electron densities in the magnetospheric trough. ¿ 1998 American Geophysical Union