OBJECTIVE: To describe the evolution of bilateral III IVH so as to define optimal dates for therapeutic moves.METHODS: Longitudinal study of brain ultrasound scans from day 1 over the first three months of life. Our team calls "massive III" a hemorrhage with an intraventricular clot diameter >8mm on the coronal view at the level of Monro's foramina of the day of maximal hemorrhage. The 90 neonates were divided into four groups. Group I included 29 premature neonates who died in the first seven days after birth (birthweight (BW), 1,114 -/+253 g, gestational age (GA), 28 weeks 3 days); with 21 massive uni/bilateral grade III PIVH, and early filling of the whole ventricular system and cisterna magna. Group II included seven premature neonates who died in the second week after birth (similar in BW and GA, but more heterogeneous group). Two groups of infants survived for more than 14 days. Group III included 30 premature neonates (BW, 1,299 -/+260 g, GA, 29 weeks 1 day), with 20 classical grade III PIVH, who had post-hemorrhagic dilatation regressed spontaneously in 13 cases and regressed after acetazolamide treatment in 17 cases (five deaths due to three bronchopulmonary dysplasias and two periventricular leucomalacias). Group IV included 24 premature neonates (BW, 1,344 -/+289 g, GA, 29 weeks 5 days) with 15 massive grade III PIVH, who suffered posthemorrhagic hydrocephalus through obstruction of the Sylvius aqueduct (15) and/or of the cisterna magna (21), 12 blocks affecting both levels. Blocks were observed from day 8, and 35 in the quasi totality of cases (17 deaths).CONCLUSIONS: From 1,183 consecutive peri-intraventricular hemorrhages (PIVH) diagnosed by brain ultrasound studies (01/01/81-12/31/94), 90 were grade (III-III) PIVH, with a 36% overall survival. The massive volume of grade III PIVG plays a heavy role in early deaths of extremely low birthweight neonates and it heralds a blocked hydrocephalus in more vigorous infants who survive PIVH.