There is a paucity of information on long-term outcome of infants who have suffered from meconium aspiration syndrome (MAS) in the neonatal period. We analyzed long-term developmental outcome data of 35 infants who were admitted to the neonatal intensive care unit (NICU) at the University of Illinois Hospital at Chicago (UICMC) with a diagnosis of MAS, and we reviewed the literature pertinent to the subject. The objective of the study was to assess the neurodevelopment status of MAS infants and compare the possible effects of different variables that are known to affect the later developmental outcome. The variables included mode of delivery, APGAR score, cord pH, mode of treatment, and neurological findings during the course of NICU. The infants were enrolled in the developmental followup program (DFUP) after discharge from the nursery for assessment of long-term developmental status and neurodevelopmental outcome. In order to assess the impact of the treatment on long-term outcome and compare our findings with previously published reports, we also reviewed the previously published literature on neurodevelopment outcome of infants treated for MAS (with different modalities) during the last three decades. Total of 35 infants with a diagnosis of MAS admitted to the NICU at UICMC were followed in the DFUP clinic for 3 years during January 1999 to September 2001. The medical records of these infants were reviewed for the mode of delivery, APGAR score, birth weight (BW), gestational age, mode of treatment during the neonatal period, and neurodevelopment status. 19/35 (54%) infants were delivered vaginally, 16/35 (46%) by cesarean section (C-section). All were treated in the delivery room using the standard resuscitation protocol. Following initial resuscitation, all except three required intubation and ventilation for varying duration. One infant required inhaled nitric oxide therapy, and two required extracorporeal membrane oxygenation treatment. Subsequent to discharge, the infants were evaluated in the clinic at 2 months of age, and then every 4 months up to 3 years. The developmental assessment of mental development index (MDI), psychomotor development index (PDI), and behavior rating scale (BRS) were obtained using the Bayley II infant motor scale, and neurodevelopment evaluation was performed using the Amiel-Tison technique. Speech evaluation was performed in infants > 18 months using the Rossetti Infant-Toddler language scale. Infants were considered normal when MDI and PDI scores were >85 to 110; mildly delayed when scores were >70 to 84; and severely delayed if the scores were <69. In addition, neurological evaluation also confirmed the disability. The report is based on the final analysis of 29 infants. Data of six infants were not included in the final analysis because of incomplete information. The mean BW of the infants was 3269 ± 671 g; mean gestational age was 39.5 ± 3.1 weeks. The median APGAR score at 1′ was 4, and at 5′ was 6. Out of 29, 11 (38%) infants were normal. Out of 29, 2 infants (7%) had cerebral palsy (CP) and 4 (14%) had severe delay at 12 months of age. Out of 29, 2 who were neurologically disabled had PDI <69. Out of 29, 12 (41%) had mild delay in speech. No statistical difference in neurodevelopment was found in infants born vaginally or by C-section. Our findings show poor outcome (CP and global delay) in 21% of infants who suffered MAS, even though the majority of the infants (26/29) responded to conventional ventilator support alone. No difference was found in the outcome of infants between NSVD vs C-section delivery. These findings suggest that infants with the diagnosis of MAS manifest later neurodevelopmental delays, even if they respond well to conventional treatment. This abstract was presented at the Society for Pediatric Research Annual Meeting, 2000.