This study investigates the effects of negotiation of meaning instances emerging from task-based synchronous computer-mediated communication (SCMC) on second language (L2) vocabulary acquisition. Results based on the chat logs produced by 20 English as a Second Language (ESL) learners collaborating on an information gap task suggest the facilitative benefits of synchronous CMC tasks for the negotiated interaction between L2 learners. Despite the split nature of negotiated interaction in the SCMC environment, most of the L2 learners were able to go through the negotiation of meaning routines...