Exploring a corpus of invitations made in telephone calls, in English (US and UK), there is evidently some variation in the turn-design in which the invitations are made. The ways in which the design form(at) of an invitation is shaped by its interactional environment and represents a particular ‘kind of occasion’ is explored here. However, there is something further which these designs tend to have in common: they are variations of ambiguous invitation forms and there is an uncertainty, a tentativeness in asking, amounting to a kind of cautiousness. This article reports these ambiguous forms via which invitations are most commonly made.