  We carry out a systematic search campaign for wide companions of exoplanet
host stars to study their multiplicity and its influence on the long-term
stability and the orbital parameters of the exoplanets. We have already found 6
wide companions, raising the number of confirmed binaries among the exoplanet
host stars to 20 systems. We have also searched for wide companions of Gl86,
the first known exoplanet host star with a white dwarf companion. Our Sofi/NTT
observations are sensitive to substellar companions with a minimum-mass of 35
Mjup and clearly rule out further stellar companions with projected separations
between 40 and 670AU.
