The hand is one of the most important instruments of our body. Its versatility enables the execution of a wide range of tasks that ask for a powerful, precise or gentle approach. Measuring hand and finger movements, and interaction forces, is therefore important for the assessment of tasks in daily life. However, measuring on-body kinematic and kinetic quantities is a delicate procedure due to the dexterity of the hand, and moreover, the little and complex shaped skin places for sensor attachment. This thesis proposes a new on-body assessment system that allows the measurement of movements and interaction forces of the hand, fingers and thumb.The first objective, the development, evaluation and validation of an inertial and magnetic sensing system for the measurement of hand and finger kinematics is the topic of chapters 2 to 5. The second objective, assessment of the dynamic interaction between human hand and environment using combined force and movement sensing, is the topic of chapter 6.Chapter 2 describes the hardware and algorithms for a sensing system which can be attached to the hand, fingers and the thumb. The hardware consists of multiple inertial and magnetic sensors to measure angular velocities, accelerations and the magnetic field. Each individual finger and the thumb is modelled as a kinematic chain where the bones correspond to the linkages and each joint is considered as an ideal ball-socket joint. Segmental lengths were determined by manual measurement, whereas the inertial sensors provided the input for a Kalman filter to estimate the 3D orientation of the corresponding segment. Hereafter, the orientation and tip position of each finger was estimated by applying forward kinematics. To our knowledge, it is the first system that uses inertial sensors for estimating finger kinematics. The estimation quality was expressed in terms of static and dynamic accuracy, dynamic range and repeatability. Differences with an active optical reference system were found to be a maximum of 13 mm for the finger tip distance difference during circular pointing movements. A standardized test protocol for instrumented gloves showed very good repeatability results compared to other datagloves, proven by the mean angle difference of < 2 degrees. Finally, a dynamic range was specified as a measure of how well the system is able to reconstruct joint angles when experiencing large angular velocities. The system showed accurate reconstruction up to 116 full index finger flex-extension movements per minute.Chapter 3 reports an extensive comparison of our inertial sensing system against a passive opto-electronic marker system. It aims on typical hand-function tasks, including tapping, (fast) finger flexion, hand opening/closing, ab-adduction and circular pointing, which are used to quantify various motor symptoms for clinical diagnosis. Three subjects were included and instrumented with both systems. Differences in position, Range of Motion (RoM) and 3D vii joint angles were noted of which the largest were found in fast and ...