The minimum corona observed with the Mark-III K-coronameter during the Whole Sun Month is compared with observations taken in June 1991 close to the last solar maximum. For both periods the three-dimensional structure of the electron density is reconstructed from coronagraph images covering a full rotation period of the Sun. This is accomplished by using methods of computer tomography specially adapted for the inversion of coronagraph images. The global structure is compared with a potential-field source-surface expansion of the photospheric magnetic field. The result affirms the model of a streamer belt around the Sun. Contrary to conventional models, however, the streamer belt shows a remarkable longitudinal density variation. A deviation between the magnetic field extrapolation and the reconstructed density enhancements occurs in the vicinity of an intense bipolar magnetic region. It can probably be attributed to the presence of nonnegligible currents in this region. We derive scale-height temperatures of 1.3 to 1.9¿106 K from selected radial density profiles for the Whole Sun Month. ¿ 1999 American Geophysical Union