To determine morbi-mortality and assess gestational age as a risk factor associated to mortality in preterm newborns. Methodology: ambispective cohort study from 2001 to 2006. Population: newborns whose gestational age is lower to 37 weeks, born alive between the first of January 2001 and the 31st of December 2006 in a third level health institution in Bogota, Colombia, whose target population is insured people associated to a private insurance company. Newborns whose gestational age was lower to 25 weeks were excluded. Sample size was 476 subjects with an expected mortality for newborns lower to 32 weeks of 8% and 2% for newborns whose gestational age was 32 weeks or more. Significance level was 0.05 and power of 80% with a relation 1:1. Sequential sampling was performed. Assessed variables included were birth year, gestational age, weight at time of birth, multiple gestations, gender, apgar, delivery way, maternal pathologies, diagnosis, interventions and complications. Analysis: early and late mortality were assessed through a uni and multivariate analysis. Results: 9273 births were obtained, 550 preterm (5.9%), male (54%). 69.45% between 33 and 36 weeks. Hypertensive maternal disease was the major cause of preterm delivery (p: 0.44). Major cause of hospital admissions were respiratory problems. Infection was the most frequent complication (33.2%) and main cause of mortality (37%). A total of 46 deaths was counted for which a neonatal mortality of 8.3x1000 was calculated. Early mortality was calculated in 63%. Conclusions: our mortality rate is similar compared to developed countries. Health policies must be improved to diminish the rate of infections, main cause of complications and mortality in our patients.