In Old Uyghur, necessity is mainly coded by means of periphrastic constructions and bound morphemes. Periphrastic constructions are formally based on verbal nominals, often combined with the word k(a)rgak ‘necessary’ and with the copulas ar- ‘to be’and tur- ‘to stand’ as well as ol ‘that’ used as a copula. Bound morphemes coding necessity are mainly based on the verbal nominal suffix {-GU}. Semantic functions of necessity markers can vary in different text groups. The study illustrates this by careful analysis of three text groups. The following types of necessity are distinguished: event-oriented, participant-oriented, and proposition-oriented. Event-oriented necessity is coded by a considerable number of markers in all text groups. Participant-oriented necessity is expressed by a limited number of markers. Proposition-oriented necessity, however, is poorly represented.