The aim of this study was to distinguish bet- ween three heuristic strategies proposed to ac- count for the assignment of ambiguous prono- uns: a subject assignment strategy, a paral- lel function strategy and a pwallel order-of- mention strategy. According to the subject assignment strategy a pronoun is assigned to a preceding subject noun phrase. A parallel function strategy predicts that a pronoun will be assigned to a noun phrase with a peirallel grzunmatical function whereas a parallel order strategy predicts that a pronoun will be a as- signed to a noun phrase in a parallel position in a previous clause. These strategies were te- sted by examining the interpretation of ambi- guous subject and non-subject pronouns. T h e results showed a bias to assign a pronoun to a preceding subject, suggesting the operation of a subject assignment strategy. However, this bias was reversed for non-subject pronouns. These pronouns showed a bias to preceding non-subjects with parallel grammatical roles, thus supporting a parallel function hypothe- sis. Finally, the subject assignment bias was reduced w h e n a non-subject pronoun had a dif- ferent grammaticaJ role from the non-subject antecedent, thus supporting a parallel order-of- mention strategy. W e conclude that all three strategies m a y constrain the assignment of am- biguous pronouns.