In this study, dynamic assessment is employed to help understand the developmental processes of two university Spanish learners as they produce a series of past narrations in a synchronous computer mediated environment. The assessments were conducted in six weekly one-hour chat sessions about various scenes of a Spanish language film. The analysis illuminates the zone of proximal development of the participants, characterizing not only their current level of independent functioning, but also their potential when provided with mediation. The utility of synchronous computer mediated communication as a medium for dynamic assessment is also discussed.