This article examines the morphosyntactic representation of the subject agreement marker (SM) in null subject constructions in the Bantu language Kinyarwanda. Three prominent analyses are compared. The first analysis treats the SM in null subject constructions as a pronoun which receives the subject theta role in the morphology. The second approach analyses the SM as a syntactic pronoun, i.e. as a determiner phrase (DP) which receives its theta role in [Spec, V] and then moves to [Spec, T]. The third analysis is based on the theory of pro, which assumes that the subject theta role in null subject constructions is assigned to a phonetically unrealised pronoun. According to the pro-theory, the SM is simply a reflex of agreement between the verb and the null subject pro. The paper shows that the first analysis, which treats the SM as a morphological pronoun, must be rejected for Kinyarwanda on empirical grounds. In contrast, the paper argues that both remaining alternatives represent feasible accounts. The study identifies the empirical predictions and theoretical consequences which are associated with each of these two competing alternatives.