The paper presents a consolidated set of principles of cooperative spoken human-machine dialogue which have the potential tor being turned into practically applicable design guidelines. The principles have been validated in three ways. They were established fi'om a Wizard of Oz simulation corpus used to develop the dialogue model for a spoken language dialogue system. Developed independently of Gricean theory, some of the principles were refined through comparison with Grice's maxims of cooperativity in conversation. Finally, the principles were tested in the user test of the implemented dialogue system. The paper shows that Grice's maxims constitute a sub-set of the principles. The nonGricean principles and dialogue aspects they introduce am presented and discussed.