  We report on 10 yr of monitoring of the 8.7-s Anomalous X-ray Pulsar 4U
0142+61 using the Rossi X-Ray Timing Explorer (RXTE). This pulsar exhibited
stable rotation from 2000 until February 2006: the RMS phase residual for a
spin-down model which includes nu, nudot, and nuddot is 2.3%. We report a
possible phase-coherent timing solution valid over a 10-yr span extending back
to March 1996. A glitch may have occured between 1998 and 2000, but it is not
required by the existing data. We also report that the source's pulse profile
has been evolving in the past 6 years, such that the dip of emission between
its two peaks has been getting shallower since 2000, almost as if the profile
is recovering to its pre-2000 morphology, in which there was no clear
distinction between the peaks. These profile variations are seen in the 2-4 keV
band but not in 6-8 keV. Finally, we present the pulsed flux time series of the
source in 2-10 keV. There is evidence of a slow but steady increase in the
source's pulsed flux since 2000. The pulsed flux variability and the
narrow-band pulse profile changes present interesting challenges to aspects of
the magnetar model.
