The mass M , and the radius R _ { h } , of the Centaurus A group are estimated from the positions and radial velocities of 30 probable cluster members .
For an assumed distance of 3.9 Mpc it is found that R _ { h } \sim 640 kpc .
The velocity dispersion in the Cen A group is 114 \pm 21 km s ^ { -1 } .
From this value , and R _ { h } = 640 kpc , the virial theorem yields a total mass of 1.4 \times 10 ^ { 13 } M _ { \sun } for the Cen A group .
The projected mass method gives a mass of 1.8 \times 10 ^ { 13 } M _ { \sun } .
These values suggest that the Cen A group is about seven times as massive as the Local Group .
The Cen A mass-to-light ratio is found to be M/L _ { B } = 155 - 200 in solar units .
The cluster has a zero-velocity radius R _ { 0 } = 2.3 Mpc .