  We present X-ray observations of the blazar Mrk501 obtained with RXTE during
1997, 1998, 1999, 2000, and 2004. The goal of this study is twofold: 1)
characterize the long-term X-ray flux and spectral variability of the source
with a model-independent analysis, and 2) investigate the X-ray and TeV
correlation on long timescales. The spectral and temporal variability
properties appear to be markedly different compared to those of
non-jet-dominated radio-loud and radio-quiet AGN monitored with RXTE. To
investigate the X-ray/TeV correlation on long timescales we compared RXTE data
with HEGRA and Whipple historical light curves. We confirm the presence of a
direct correlation, which appears to be stronger when the source is brighter.
The analysis of individual flares shows that the X-ray\TeV correlated activity
is heterogeneous. However, more sensitive TeV observations are necessary to
confirm these findings, and to put tighter constraints on jet models
(abridged).
