Placenta accreta is an abnormally firm attachment of placental villi to the uterine wall, which may cause postpartum hemorrhage resulting in maternal morbidity and mortality. The purpose of the present study was to clarify the incidence, clinical background and prognosis of placenta previa increta/percreta treated with different modalities in Japan. Medical records of cases with placenta previa increta/percreta in eight tertiary centers between January 1994 and December 2004 were reviewed. Placenta accreta without actual invasion into the myometrium confirmed by pathology was not included in placenta increta/percreta. Details of obstetric history, maternal background, ultrasonographical findings, the course of delivery, subsequent complications and management were noted. Among the total of 59,008 deliveries, 45,261 were by the vaginal route (76.7%) and 13 747 by cesarean section (23.3%). In this study, 408 cases were diagnosed as placenta previa (0.69%), 18 of these being placenta increta and 5 placenta percreta. Only 1.1% of cases of placenta previa without prior cesarean section were increta/percreta, in contrast to 37% of placenta previa after prior cesarean sections. Mean intraoperation blood loss was 3630 +/- 2216 g (increta) and 12,140 +/- 8343 g (percreta). One patient with placenta previa percreta died of hemorrhage. Stepwise treatment (cesarean section without separation of the placenta, arterial embolization and hysterectomy) was applied for 4 cases, which had the least blood loss. Placenta previa increta/percreta is a life-threatening disease. Patients who undergo hysterectomy after uterine arterial embolization demonstrate reduced intraoperation blood loss, and this treatment should be incorporated to reduce maternal morbidity.