  We present ASCA and ROSAT observations of the Be/X-ray binary pulsars RX
J0146.9+6121 and X Persei between 1990 and 1996. Measuring the neutron star
spin period and X-ray luminosity of X Persei shows that the episode of low
X-ray luminosity and monotonic spin-down since 1978 continued to at least
August 1995. ASCA and ROSAT HRI observations of RX J0146.9+6121 detected the
pulsar with the longest known neutron star spin period at low luminosities
after the X-ray outburst seen by EXOSAT in August 1984. The large spin period
decrease seen between 1984 and 1993 has nearly stopped at a period of 1407.3 s
in February 1996. We discuss that the X-ray outburst behaviour of X Persei with
respect to its Be star phase changes observed in the optical can be caused by
an asymmetry in the matter distribution around the Be star.
