Background: Fortification of wheat flour with folic acid in Chile, started in January 2000. This fortification should decrease the incidence of neural tube defects. Aim: To study the incidence of neural tube defects among Chilean newborns, during 1999. Material and methods: The records of all newborns and stillbirths with a birth weight over 500 g from 9 public maternity hospitals in Santiago in 1999, were reviewed. All neural tube defects, associated or not to other malformations were taken into account. Results: During the study period, 59.627 newborns and 455 stillbirths were analyzed. The global incidence of neural tube defects was 1.56 per 1.000 born (57% women, 42% men and 1% ambiguous sex). Spina bifida was the most frequent neural tube defect found. Conclusion: These baseline data will be useful to assess the impact of folic acid fortification of wheat flour. (Rev Méd Chile 2001; 129: 277-84).