It is not uncommon for parties to a contract to agree to assume a qualified obligation. The obligation may be to use one’s “best endeavours”, “reasonable endeavours” or “all reasonable endeavours” to achieve a stated objective. What exactly do these obligations entail has generated a body of case law but their distinction is still far from clear. This article examines how these obligations have been interpreted by the courts in England, Australia and Hong Kong, in the hope that they may shed some light on how such terms may be interpreted in the future by a Hong Kong court.