This study investigated whether a structured communication interface fosters primary students' communicative competence in a synchronous typewritten computer-mediated collaborative learning environment. The structured interface provided a set of predetermined utterance patterns for elementary students to use or imitate to develop communicative competence including comprising grammatical, sociolinguistic, discourse and strategic competence. Two intact classes of fifth graders; each with 33 students, participated in this study. The students in each class were randomly arranged into triads. Members of a triad were designated to separate computers, seated at a proper distance and required to collaboratively accomplish a shared learning task (concept mapping). One class was provided the structured communication interface. The other class used a generic (non-structured) interface. It was found that students who used the structured communication interface had significantly better communicative competence development, especially in strategic competence and discourse competence, than students using the unstructured condition. In addition, students using the structured interface continued to demonstrate better collaborative productivity. (Contains 2 tables and 3 figures.)