Abstract.We conducted two studies on the use of null and overt pronouns and noun phrases in Vietnamese, with a focus on referents' grammatical roles, grammatical parallelism and topicality. Vietnamese overt pronouns differ from English-type languages as they also function as kin terms. The first study investigated narratives and finds that referential form choice is influenced by the grammatical role and grammatical position of the antecedent: When the subject of the current clause refers to the subject of the preceding clause (subject parallelism), we find a high rate of (null and overt) pronouns. Lack of parallelism triggers mostly NPs. When the object of the current clause refers to the object of the preceding clause (object parallelism), we also find more pronouns than in non-parallel cases. Interestingly, null pronouns only occur in parallel cases. Crucially, we find no clear differences in the distribution of null vs. overt pronouns, suggesting that grammatical roles and parallelism have the same effects on both pronoun types. Using passivization to manipulate topicality, Experiment 2 further investigated the null vs. overt pronoun choice and found that pronouns are strongly preferred for topicalized subjects in passives and that null pronouns exhibit a stronger sensitivity to topicality than overt pronouns. To our knowledge, these experiments are the first experimental investigation of a kin-termbased pronoun system.