In order to efficiently digitize the 3-D shape of objects in applications such as quality control, reverse engineering and inspection, a flexible system based on a portable range sensor coupled to an optical tracking device has been developed. The hand-held range sensor can be moved freely in space without the constraint on motion imposed by a translation or rotation system. An optical tracking device synchronized with the sensor is used to compute the sensor's orientation and location in real-time. The optical tracking and the integration of a 3-D range sensor with a positioning device for manual scanning constitute the two major challenges of the proposed system. This paper first presents the range sensor and the optical tracking system. The main aspects including the calibration approach and the sensor integration are described in the following sections. An error analysis has been conducted to predict the expected results. Finally, experimental results are presented to validate the overall system.