AbstractBackground. The aim of this study was to investigate the clinical effectiveness of a structured group intervention program for Japanese patients with breast cancer. Methods. Fifty-seven patients with breast cancer participated in this program. The scores for the Profile of Mood States (POMS) and the Dealing with Illness Inventory were compared before and after intervention. As 5 patients failed to complete the program and 5 did not complete the inventories, the results for 47 patients were analyzed. As intravenous chemotherapy was presumed to cause severe distress, 7 patients who received this treatment during the period covered by the sessions were excluded. The scores of the remaining 40 patients were compared. Results. In the 40 patients, there were significant differences between the before and after intervention scores for Depression, Lack-of-Vigor, Tension-Anxiety, Confusion, and Total Mood Disturbances. Scores for coping strategies and methods, such as passiveresignation, cognitivepassive/ruminative, and avoidance were decreased, as expected; however, scores for activeexpressive/information-seeking, and activereliance on others were, unexpectedly, decreased. Conclusion. This study demonstrated the short-term effectiveness of structured interventions for Japanese patients with breast cancer, especially in alleviating psychological distress.