BACKGROUND: To evaluate the treatment and neonatal outcome in pregnancies complicated by twin-twin transfusion syndrome (TTS). MATERIAL AND METHODS: Twenty-four women with TTS were identified in the period 1993-99 among 34477 deliveries. We include a retrospective chart review of all twins with TTS. RESULTS: The overall incidence of TTS was 4.75% of all twin pregnancies. The mean gestational age at the time of diagnosing TTS was 23 weeks (range 17.6-38), and the mean gestational age at delivery was 34.6 weeks (range 23.1-38.3). Therapeutic amniocenteses was performed in 21 women. The total volume drained varied from 0.4 to 32.31 with a mean of 2.3 l. Overall perinatal mortality in TTS was 35.4%, as nine donor twins and eight recipient twins died. The main causes for mortality were intrauterine death and prematurity. CONCLUSION: Twin-twin transfusion syndrome is a severe complication in monochorionic diamniotic twin pregnancies, with high perinatal mortality and morbidity even though amnioreduction prolonged the pregnancies leading to better neonatal outcome.