We present sensitive , high angular resolution ( 6 ^ { \prime \prime } \times 5 ^ { \prime \prime } ) \lambda 21-cm observations of the neutral hydrogen in the nearby barred Seyfert galaxy , NGC4151 .
These HI observations , obtained using the VLA in B-configuration , are the highest resolution to date of this galaxy , and reveal hitherto unprecedented detail in the distribution and kinematics of the HI on sub-kiloparsec scales .
A complete analysis and discussion of the HI data are presented and the global properties of the galaxy are related to the bar dynamics presented in Paper I .

HI absorption , consistent with previous studies , is detected against the radio continuum nucleus and shows two components – a deep absorption component , centred at 987 \pm 1 km s ^ { -1 } and width 87 \pm 3 km s ^ { -1 } , and a weaker component , redshifted to 1096 \pm 6 km s ^ { -1 } with a width of 35 \pm 15 km s ^ { -1 } .
An alternative fit is also presented .
In addition to the absorption , a high velocity cloud is detected in emission , coincident with the nucleus .
This cloud is red-shifted by 260 km s ^ { -1 } from systemic , has an HI mass of 2.3 \times 10 ^ { 7 } M _ { \odot } , and corresponds to outflow on the far side of the nucleus .

Contrary to previous studies , no HI bridge is detected reaching from the shocks directly across the nucleus .
Instead , the gas streams from the shocks onto smaller orbits and forms fingers of HI which wind around the nucleus , consistent with predictions from general numerical simulations of bars .
These fingers correspond closely with dust arcs seen in optical studies and resemble nuclear features seen by others in weak barred galaxies such as M100 .

A new rotation curve is presented , extending to within 8 ^ { \prime \prime } of the nucleus and showing a turnover at a radius of \sim 35 ^ { \prime \prime } , which was previously undetected in lower resolution studies .
The corresponding resonance curve and the properties of the shocks ( Paper I ) yield a bar pattern speed of 24.5 \pm 3.7 km s ^ { -1 } and one Inner Lindblad Resonance ( ILR ) at a radius of 2.8 \pm 0.6 kpc .
Our observations , however , do not rule out the possibility of an Inner ILR .