Between 1995 and 2003 the Doppler on Wheels (DOWs) mobile radar systems have observed over 40 tornadoes at close range. The Doppler velocity measurements of these tornadoes exhibit a large variation in the size, intensity, and structure of the core-flow and surrounding region. The spectrum of observed tornado core-flow structures includes velocity fields consistent with a one-cell vortex, a two-cell vortex, or an intermediate state between these two vortex models. A comparison is established between the velocity fields of several prominent tornadoes observed by the DOWs to quantify the structural differences between the apparent one-cell and two-cell tornadoes. This comparison includes differences in core-flow size, peak tangential velocities, tangential velocity gradients, and motions of any vortices on a scale smaller than the primary tornado vortex. These Doppler velocity tornado characteristics are also compared with concurrent Doppler velocity measurements from local WSR-88Ds.