  We present the BeppoSAX observations of 3C 279 performed in 1997 January
13-23 simultaneously with gamma-ray pointings with EGRET on board CGRO and
optical observations at the Torino Observatory (1997 January 11-18). ISO data
close to this epoch are also available. We compare the derived Spectral Energy
Distribution with those obtained at all other epochs with adequate
multiwavelength coverage. Simple spectral models fitted to the multiepoch SEDs
suggest that changes in intensity can be ascribed mainly to the variation of
the bulk Lorentz factor of the plasma in the jet.
