This article describes the implementation of the cooperative development (CD) technique by two professors at a Japanese university. With this technique, colleagues work together by adopting the roles of "speaker" and "understander" to support each other's process of addressing teaching concerns. The skills required for CD include exploration (subdivided into attending, reflecting, and focusing, skills for the understander to use in supporting the speaker), discovery (divided into thematizing, challenging, and disclosing), and action (including goal-setting, trialling, and planning) for instructional change. The report describes the institutional and classroom context of the work, outlines the principles and procedures of CD, analyzes the most interesting aspects of what was accomplished, and evaluates the CD process by summarizing key learning experiences and making suggestions for further improvement. Meetings between the two colleagues were taped and transcribed, and some excerpts are included here. (Contains 13 references). (MSE)