One of the most sensitive issues in K-12 education today is that of professional negotiations between administration and teachers. This paper describes the effects of mediation training on negotiation talks between teachers and management. Teams of representatives from a teachers' union and a board of education participated in a 1-week mediation training session based on the Federal Mediation Conciliation Service (FMCS) negotiation model. They then engaged in a negotiation process that lasted over 2 years. Data were obtained through participant observation, focus-group discussions, and interviews. Although the training process produced changes in participants' behaviors, some participants continued to exhibit a great resistance to change. Both a formal and an informal power structure continued to operate, which was evidenced by representatives' use of jargon and terminology specific to their group or school. Some participants violated the ground rules by holding private "caucuses" to discuss issues. In short, some participants reverted to the old behaviors and attitudes of mistrust and partisanship. The findings suggest that the brief initial training was not sufficient for team members to internalize the interest-based bargaining process and that periodical retraining is necessary for true and lasting change to occur. One figure is included. (Contains 37 references). (LMI)