This study describes intra-hospital survival rates of very-low-birth-weight infants, as well as factors present at birth associated with survival, during a period of 10 years. This is a Retrospective cohort study performed in a 3rd level nursery at Santa Joana Maternity Hospital, a fee-paying institution in Sao Paulo, Brazil. From January 1991 to December 2000, 963 live-born infants with a birth weight of 500-1499 g, without congenital anomalies, were followed until discharge. Survival was studied according with year of birth, and stratified by birth weight and gestational age. Factors present at birth associated with survival were analyzed by logistic regression. Patient characteristics were: birth weight 500-999 g (38%), gestational ages <or=27 weeks (32%), prenatal care (100%), small for gestational age (39%), multiple gestation (22%), male (52%) and C-section (68%). According to birth weight 500-749, 750-999, 1000-1249 and 1250-1499 g, survival rate in 1991 was, respectively, 0, 6, 60 and 80% and increased to 15, 71, 93 and 96% in 2000. Regarding gestational age of 24-25 weeks, 26-27 weeks and 28-31 weeks, intra-hospital survival in 1991 was 0, 0 and 57%, and in 2000, improved to 44, 74 and 82%. Survival was associated with increasing birth weight (OR 0.996; CI 95%: 0.995-0.997) and gestational age (OR 0.73; CI 95%: 0.67-0.80), female gender (OR 1.52; CI 95%: 1.04-2.22) and year of birth (OR 0.70; CI 95%: 0.65-0.76). In the 1990s, survival rates among very-low-birth-weight infants improved according to year of birth, mainly in female patients with birth weight >or=750 g, and gestational age >or=26 weeks.