  We present the spectral and timing evolution of the persistent black hole
X-ray binary GRS 1758-258 based on almost 12 years of observations using the
Rossi X-ray Timing Explorer Proportional Counter Array. While the source was
predominantly found in the hard state during this time, it entered the
thermally dominated soft state seven times. In the soft state GRS 1758-258
shows a strong decline in flux above 3 keV rather than the pivoting flux around
10 keV more commonly shown by black hole transients. In its 3-20 keV hardness
intensity diagram, GRS 1758-258 shows a hysteresis of hard and soft state
fluxes typical for transient sources in outburst. The RXTE-PCA and RXTE-ASM
long-term light curves do not show any orbital modulations in the range of 2 to
30 d. However, in the dynamic power spectra significant peaks drift between
18.47d and 18.04d for the PCA data, while less significant signatures between
19d and 20d are seen for the ASM data as well as for the Swift/BAT data. We
discuss different models for the hysteresis behavior during state transitions
as well as possibilities for the origin of the long term variation in the
context of a warped accretion disk.
