  Spectra taken with the Space Telescope Imaging Spectrograph (STIS) allow
accurate location and extraction of the nuclear spectrum of NGC 4151, with
minimal contamination by extended line emission and circumnuclear starlight.
Spectra since 1997 show that the P Cygni Balmer and He I absorption seen
previously in low nuclear states, is present in higher states, with outflow
velocity that changes with the nuclear flux. The phenomenon is discussed in
terms of some of the absorbers seen in the UV resonance lines, and outflows
from the central source and surrounding torus.
