The applicability of the H∞ control technique to a fully actuated 3D biped robot is addressed. In contrast to previous studies, this investigation contributes to the study of robustness of bipedal locomotion while assuming an imperfect knowledge of the restitution rule at the collision time instants in addition to external disturbance forces applied during the single support phases. Performance issues are illustrated on a numerical study performed on the 32-DOF biped robot ROMEO, of Aldebaran Robotics.