We present the results of an analysis of the ultraviolet and X–Ray variability of the Broad–Line–Radio Galaxy 3C390.3 over 15 years .
The UV continuum of 3C390.3 showed large variations with amplitudes of up to a factor of 10 .
We find :

( 1 ) The variations of CIV and Ly \alpha are highly correlated with the UV continuum , and are delayed with respect to the continuum variations by 50–110 days with the red wing of both CIV and Ly \alpha , leading the blue wing ;

( 2 ) The CIV/ Ly \alpha ratio is positively correlated with both the continuum flux and UV line strength , a behavior different from other AGNs studied so far ;

( 3 ) The blue sides of the Ly \alpha and CIV profiles are similar to the blue side of the Balmer lines , while the red sides are different , suggesting a different origin for the red peak in the Balmer lines .

The X–Ray spectra of 3C390.3 observed with ROSAT can be well fitted by a single power-law at Galactic absorption with a spectral slope of \alpha = 0.9 .
The overall optical , UV to X–Ray spectrum can also be described by a single power law with \alpha _ { uvx } = 0.89 , indicating a very weak or no big blue bump .
The unusual behavior of CIV/ Ly \alpha variations might be related to this hard ionizing continuum in 3C390.3 .

Our results suggest : ( 1 ) The broad CIV and Ly \alpha emitting gas is infalling towards the central object in 3C390.3 ; ( 2 ) The overall behaviour of the CIV/ Ly \alpha ratio and the absence of a big blue bump , strongly indicate the coexistence of optically thick as well as optically thin BLR clouds ; ( 3 ) Assuming circular symmetry and predominantly circular motion , the BLR gas is situated at 83 \pm 25 lightdays from the central source ; ( 4 ) Under these assumptions and with the derived circular velocity of v _ { rot } \simeq 2850 km s ^ { -1 } , the central mass inside this radius is confined to 1.3 ~ { } 10 ^ { 8 } M \odot < M _ { CM } < 4.0 ~ { } 10 ^ { 8 } M \odot ; ( 6 ) Comparing our results with those obtained from VLBI and observations of the Fe K \alpha line , suggests the association of the BLR with a disk , inclined at 98 \pm 12 degrees with respect to the direction of superluminal motion of the radio blobs .