We report the detection of a cyclotron absorption line and its second harmonic in the average spectrum of the high mass X-ray binary 4U1907+09 observed by the BeppoSAX satellite on 1997 September 27 and 28 .
The broad band spectral capability of BeppoSAX allowed a good determination of the continuum against which the two absorption features are evident at \sim 19 and \sim 39 keV .
Correcting for the gravitational redshift of a \sim 1.4 M _ { \odot } neutron star , the inferred surface magnetic field strength is \mathrm { B } _ { surf } = 2.1 \times 10 ^ { 12 } G that is typical for this kind of systems .
We also detected an iron emission line at \sim 6.4 keV , with an equivalent width of \sim 60 eV .