Increasing attention has been given to Paired Assessment (PA), in which two second language (L2) learners work as status-equal interlocutors to demonstrate their L2 proficiency. Claims have been made that the status-equal format of a PA can provide useful data on a wide range of linguistic and sociolinguistic abilities. These abilities are more typically assessed through interviews, protocols, and questionnaires administered by a test provider who serves in a high authority capacity. PA research findings have been informative with respect to the characteristics of activities that can be used to provide valid and reliable performance data. However, the findings on interlocutor characteristics have been conflicting, a situation that has been attributed to methodological inconsistencies within and across relevant studies. Of critical concern is whether the a lower, higher, or equal L2 developmental level of a test-taker vis-a-vis that of the paired partner will yield consistent performance results. This concern is of theoretical importance with respect to the role of PA in tracking developmental change. It also holds practical importance, as PA is often carried out in classrooms, where there are often differences among learners in their developmental levels. These issues and concerns provided the impetus for this dissertation research. Results of the study revealed that 1) ETTs’ ability to produce linguistically accurate utterances did not vary regardless of their NETTs developmental stages. This result was consistent to that of their test-raters’ evaluation. 2) ETTs’ ability to interact in ways that are sociolinguistically appropriate and interactionally strategic did not vary regardless of their NETTs’ L2 developmental stages. However, the test-raters’ evaluation of ETTs’ performance in this dimension revealed variation depending on NETTs’ L2 developmental stages. These results shed light on 1) the extent to which there is variation in ETTs’ linguistic and sociolinguistic performance in relation to NETTs’ L2 development; 2) the role of PA in providing data that can contribute to a valid and reliable assessment battery; 4) the value of PA as a classroom assessment as well as high-stakes testing instrument.