The design and development of GRACILE, a collaborative learning environment in the domain of Japanese language patterns and expressions, is described. The environment is designed to allow learning goals communication, learning activities negotiation, and collaboration between learners. From a group of student models, a potential development level is represented for each learner, representing the knowledge the learner can reach with the assistance of more experienced peers or a teacher. The student model represents the learner's actual development level, by a set of patterns and expressions which appear in correct sentences constructed by the learner, without any help from the system or other colleagues. GRACILE cooperates with each learner, generating the respective student's knowledge frontier, which is defined with respect to the knowledge of other learners and the more complex language patterns which the system believes have already been internalized by the student. The environment provides the learners with a toolbox for dialogue construction, including dictionaries. A set of dialogue agents, whose capabilities are the construction and appropriate use of language patterns and expressions in different dialogue situations, may also be requested for help. During sentence construction, learners can be assisted by other learners. The "Learners Performance Communication" module allows the student free access to open models which represent the group members' actual development level, thereby allowing the learner to locate their own level in relation with the others', and encouraging the learner to realize who can help him/her or who can be helped. It is believed that GRACILE will help Japanese language students develop reading and writing skills faster, allowing them to become more productive at communicating. (Contains 16 references.) (MAS)