We investigated the effects of psychiatric group intervention on the emotions, natural-killer (NK) cell activity and pregnancy rate in Japanese infertile women by a randomized study. Thirty-seven women completed a 5-session intervention program and were compared with 37 controls. Psychological discomfort and NK-cell activity (47.7% to 34.1%, P<.0001) significantly decreased after the intervention, whereas no significant changes were observed in controls. According to a 1-year follow-up of both groups, the pregnancy rate in the intervention group was significantly higher than that of controls (37.8% vs. 13.5%, P=.03). Psychological group intervention was therefore effective in Japanese infertile women.