  Very Long Baseline Polarimetric observations of the Broad Line Radio galaxy
3C111 performed in July and September of 1996 at 8 and 43 GHz reveal rapidly
evolving parsec-scale radio structure after a large millimetre outburst. The
B-field geometry is not simple. We present a first analysis of possible Faraday
and optical depth effects based on a comparison of the polarization images for
the two frequencies.
