In a cohort study from 1983-1993, we compared the neurodevelopmental outcome of 31 consecutive neonatal survivors of 35 gestations withmonochorionic-diamnionic placentation complicated by twin-twin transfusion syndrome (TTS) with that of 62 twin survivors ofdichorionic-diamnionic placentation. TTS cases and controls were matched for gestational age, year of birth and sex. Outcome was assessed at 4, 8, 12, 18, 24 months adjusted age (AA) using the Amiel-Tison Neurologic Screen and the Gesell Developmental Screening Inventory. The diagnosis of TTS was based on clinical (discordant growth, polyhydramnios, &/or hematocrit differential) and pathological (A-V anastomoses) evidence. Mortality included 1 postnatal, 15 neonatal and 8 fetal deaths. Fifteen infants were lost to follow-up. TTS survivors and controls were similar in gestational age (30 wks), incidence of RDS (56 vs 50%), IVH (Grade 1-4: 41 vs 56%), and CLD (17 vs 11%). Between 4-10 months, neurodevelopmental outcome was similar in TTS cases and controls. At ≥ 12 mo AA, 23 TTS and 60 controls were evaluated (mean AA=20 mos). At the time of last exam for this group, TTS cases were as likely as controls to have normal mental (67 vs 83%), motor (76 vs 78%) and neurologic (65 vs 78%) outcomes; although, their mean composite mental score was lower (87±15 vs 96±12, p=.004). The incidence of cerebral palsy, 11% overall, was not significantly higher in TTS survivors (22 vs 7%, NS). Neonatal variables which independently increased the risk of abnormal neurodevelopmental outcome included abnormal neonatal neuroimaging (OR=3.4, p=.002), but not the presence of TTS. Summary: Although perinatal morbidity and mortality associated with twin-twin transfusion syndrome is high, early childhood neurodevelopmental outcome of TTS survivors is similar to that of matched twin control infants.