The goal of this work is to present the results of an experimental study of impedance control schemes for a robot manipulator in contact with the environment. Six-degree-of-freedom interaction tasks are considered which require the implementation of a spatial impedance described in terms of both its translational and its rotational part. Two representations of end-effector orientation are adopted; namely, Euler angles or quaternions, and the implications on the choice of different orientation displacements are discussed. The controllers are tested on an industrial robot with open control architecture in a number of case studies.