The recent experimental realization of chromium Bose-Einstein condensates 
has encouraged research on the new field of dipolar gases at very low 
temperature. While the $s$-wave contact interaction is isotropic, the 
dipolar interaction is anisotropic and long-range, giving rise to 
interesting phenomena in dipolar condensates. These gases constitute a 
unique testing ground of the interplay between different interatomic 
interactions in the superfluid properties, in particular in quantized 
vortex states. We investigate the properties of a singly quantized vortex 
and calculate the critical angular velocity for different values of the 
s-wave scattering length. The energy barrier for the nucleation of a 
vortex is calculated as a function of the vortex displacement from the 
rotation axis.