A study investigated the effectiveness of full dyadic writing as a technique for teaching writing to students of English as a Second Language (ESL). Subjects were 31 college students of diverse cultural backgrounds enrolled in ESL sections of freshman English. Each chose a partner with a different native language with whom to write two essays, the first and fifth of the course. For the first, three pairs volunteered to have the entire writing process videotaped for closer observation. Scores on the first dyadic essay were compared with the second essay of the course, written individually, and scores on the second dyadic essay were compared with individual scores of the fourth essay of the course. Students also recorded reactions to collaborative writing after each dyadic essay. Results indicate students performed better on the first dyadic essay than on the subsequent individual essay, but showed no gain in the second dyadic essay over the other individual assignment examined. The taped dyads showed very different dynamics of cooperation. Responses to the first dyadic assignment were overwhelmingly positive. Comments on the second dyadic assignment were more general and included more negative reactions. The technique is seen as useful for both teaching and research. (MSE)