The kinematics of wheeled mobile robots (WMRs) equipped with an arbitrary number of either conventional orientable wheels or dual-wheel units (DWUs) is the subject of this paper. The configuration of a robot with s such, wheels is defined by 3 + 2s variables, three for the platform configuration and two for each single wheel or dual-wheel unit. However, not all variables related to the wheel configuration are independent since, for the platform to be able to undergo an arbitrary planar motion, the wheel-unit configurations must satisfy s − 2 compatibility conditions. Therefore, the number of independent variables which defines the degree of freedom (dof) of the system is 3 + 2s − (s − 2) = s + 5. On the other hand, it is made apparent that wheeled mobile robots equipped with at least three orientable wheels have three independent generalized velocities. Hence, the mobility of these robots, which is defined as their number of independent generalized velocities, is three; in other words, they are of full mobility.