  We intended to measure the radial velocity curve of the supergiant companion
to the eclipsing high mass X-ray binary pulsar EXO1722-363 and hence determine
the stellar masses of the components.
  We used a set of archival K$_{\rm s}$-band infrared spectra of the
counterpart to EXO1722-363 obtained using ISAAC on the VLT, and
cross-correlated them in order to measure the radial velocity of the star.
  The resulting radial velocity curve has a semi-amplitude of $24.5 \pm 5.0$ km
s$^{-1}$. When combined with other measured parameters of the system, this
yields masses in the range 1.5 $\pm$ 0.4 - 1.6 $\pm$ 0.4 M$_{\odot}$ for the
neutron star and 13.6 $\pm$ 1.6 - 15.2 $\pm$ 1.9 M$_{\odot}$ for the B0--1 Ia
supergiant companion. These lower and upper limits were obtained under the
assumption that the system is viewed edge-on (i = 90$^\circ$) for the lower
limit and the supergiant fills its Roche lobe ($\beta = 1$) for the upper limit
respectively. The system inclination is constrained to $i>75^{\circ}$ and the
Roche lobe-filling factor of the supergiant is $\beta>0.9$. Additionally we
were able to further constrain our distance determination to be 7.1 $\le$ d
$\le$ 7.9 kpc for EXO1722-363. The X-ray luminosity for this distance range is
4.7 $\times$ 10$^{35}$ $\le$ L$_{\rm X}$ $\le$ 9.2 $\times$ 10$^{36}$ erg
s$^{-1}$.
  EXO1722-363 therefore becomes the seventh of the ten known eclipsing X-ray
binary pulsars for which a dynamical neutron star mass solution has been
determined. Additionally EXO1722-363 is the first such system to have a neutron
star mass measurement made utilising near-infrared spectroscopy.
