A one sample pre-post design was used simultaneously with three work groups to study the effects of a health team development intervention on interdisciplinary (ID) team processes. Effects were measured by participant questionnaires, managerial diagnostic and follow-up interviews, and by direct observation of team meetings. The intervention, as conducted by internal facilitators, was published in Improving the Coordination of Care: A Program for Health Team Development by Rubin, Plovnick, and Fry. Positive changes were found in members' perceptions of their team's general effectiveness, their leader's approachability, and the value of their meetings. No changes were found in member participation and influence, however, when pre-post differences were compared using the Dunn-Bonferroni approach to multiple t-tests on nine Mean Factor Difference Scores of the Group Behavior Inventory. Structured observation data showed increases in proportional frequencies of Interpretative statements, Alternatives suggested, and Decisions made during teams' meetings. Questions asked and Information given categories on the Team Observation Protocol data showed decreases. No change occurred on the two seldom-used categories, affective statements about Client and Team. Pre-intevention diagnostic interviews had shown that senior management's and team facilitators' expectations were congruent with the goals, roles and procedural areas targeted for change by the team development program. However, Follow-up interviews corroborated prior organization development research. That is, a comprehensive organizational diagnosis of teamwork problems was needed prior to the selection and implementation of team development with ID teams. Especially sensitive areas for management-consultant negotiation in future efforts to implement HTD should include the use of internal or external third party facilitators, the selection of teams, role of team leaders, and the adaptation of materials and activities to suit ID team tasks. Where conflict exists between senior management and team leaders, other interventions may be needed before team development can be expected to affect positively, ID team members' participation and involvement. Recommendations were made for structural changes to strengthen ID teamwork at the training center. The absence of an empirically-derived theory of ID team performance effectiveness continues to be a barrier to the demonstration of intervention effects and to education for teamwork. Research is needed to describe empirically relations between problem-solving processes in ID team meetings and treatment decisions. Research is also needed to delineate team-role competencies required by members and leaders as prerequisites to establishing indicators of ID team performance effectiveness.