Objective: To describe the neonatal and maternal outcome of macrosomic infants weighing at least 4000 grams. Study Design: Case control, retrospective study. Maternal and neonatal records of infants weighing at least 4000 g (n = 1000) at birth were identified between 1988 and 1992. One thousand cases among the newborns delivered with birthweights between 2500-4000 g in the same period were randomly chosen and reviewed as a control group. The obstetrical outcome variables ot the groups including the mode of delivery and incidence of maternal and perinatal complications were compared. Results: There were 16,112 deliveries during the study period in our institution. Macrosomic infant rate was 6.21%. Mean (± stantard deviation) birthweight for the study group was 4272 ± 239 g and 3277 ± 316 g for the control group (p < 0.001). The overall cesarean section rate was 28.8% in the study group (p < 0.001). In the study group, seventeen cases of brachial plexus palsy (2.4%) and sixteen cases of clavicular fracture (2.3%) and one case of humerus fracture (p < 0.001) was observed. Perinatal mortality rate of the macrosomic infant group was 0.8% and there were fourteen cases (1.4%) of asphyxia related to delivery in macrosomia group (p < 0.01). The rate of maternal complications with macrosomia including genital lacerations requiring repair and uterine atony were significantly higher than those of controls (p < 0.01). Conclusion: The infants with a birthweight of at least 4000 g are at increased risk for birth trauma and asphyxia. The risk of birth trauma in the infants with a birthweight of 4500 g or more is significantly higher than those with a birthweight of 4000-4499.