  We present pulse phase resolved spectra of the hypergiant high mass X-ray
binary GX 301-2. We observed the source in 2001 October with RXTE continuously
for a total on-source time of almost 200ksec. We model the continuum with both,
a heavily absorbed partial covering model and a reflection model. In either
case we find that the well known cyclotron resonant scattering feature (CRSF)
at 35keV is - although present at all pulse phases - strongly variable over the
pulse: the line position varies by 25% from 30keV in the fall of the secondary
pulse to 38keV in the fall of the main pulse where it is deepest. The line
variability implies that we are seeing regions of magnetic field strength
varying between 3.4 10^12G and 4.2 10^12G.
