A study of the velocity field of NCC 7331, an Sb spiral like M31, has been made from nine spectra. The corrected recession velocity is + 1082 km/sec. Out to a distance of 143" from the center (10 kpc) the rotation-curve is generally well defined, but beyond that point (to 250") all velocities are low. We assume that in these outer regions non-circular motions are present The mass within 10 kpc is 8 X 1010 M0 the mean density is 1 6>( 10-" gm/cm'. The rotation-curve has been extended beyond 10 kpc by using the density distribution interior to that point and limiting cases for the density beyond that point. It is shown that the total mass may be as large as 1 4 X 1011 M0 Since M = -212, L = 4.6 X 1010 L0, and for the region within 10-kpc radius of the center, M/L = 2. Although the dimensions, magnitude, and mass distribution of NCC 7331 are similar to those in M31, the mean density is less by a factor of 2 or 3.