  We present milliarsecond-resolution maps of the SiO maser emission v=1 J=2-1
(3 mm) in the bipolar post-AGB nebula OH231.8+4.2, and compare them with our
previous observations of the v=2 J=1-0 line (7 mm). Our observations show that
the SiO masers arise in several bright spots forming a structure elongated in a
direction perpendicular to the symmetry axis of the nebula. This, and the
complex velocity gradient observed, is consistent with the presence of an
equatorial torus in rotation and with an infall of material towards the star.
