This paper deals with the design process of a particular mechatronic system: a tele-echography robot. First, we describe the principle of robotized tele-echography and the prototypes already designed. Then, after having chosen the design process, we show two medical gestures analysis performed to define the required specifications of a tele-echography robot. Several kinematic synthesis allow demonstrating that the serial spherical wrist is the most adapted structure to this medical application. The kinematic performance of this structure is limited by the singularity position located at the centre of the workspace. An inclined spherical wrist structure is proposed to displace the singularity position in a less used workspace zone that the normal direction to the patients skin. In the dimensional synthesis phase, this structure is optimized. Then, a collaborative design study with designers is presented to improve aesthetic and ergonomic of the robot. This step was very interesting because it brought innovative propositions. Finally, a detailed phase allows defining the PROSIT 1 robot. It was manufactured and will be soon tested in clinical environment.