Base deficit and serum lactate concentrations may be important prognostic indicators in preterm infants. We sought to (1) determine the relationship between day 1 serum lactate values and base deficit and (2) determine the relationship between day 1 biochemical parameters and adverse outcome in preterm infants <32 weeks. This was a retrospective study of all patients less than 32 weeks gestation admitted to neonatal intensive care unit over a 6-month period. All blood gases performed during the first 24 h post delivery were analysed. Adverse outcome was defined as death, severe (grade 3 or 4) intraventricular haemorrhage or periventricular leukomalaica on cranial ultrasonography. Patients were excluded if there was a known lethal malformation or cardiac defect. Seventy-two infants had a total of 473 lactate levels performed in the first 24 h. Mean (SD) gestational age was 29 (2.3) weeks, mean (SD) birth weight 1.28 (0.42) kg. Mean (SD) lactate values in first 6 h was 4.63 (3.69), at 12 h 3.08 (2.6), at 18 h 2.47 (2.68) and 2.08 (2.74) mmol/l at 24 h. There was a strong correlation between lactate values and base deficit values (R value 0.8, p < 0.01). Mean base deficit values at 6 h were 5.9 (4.5), at 12 h 3.8 (3.9), at 18 h 3.6 (3.1) and at 24 h 4.1 (3.8) mmol/l. A single lactate value greater than 5.6 mmol/l had a sensitivity of 100% and specificity of 85% of identifying adverse outcome. Persistently elevated or worsening lactates were associated with adverse outcome. There is a strong correlation between lactate values and base deficit on day 1 of life. Serial lactate measurements greater than 5.6 mmol/l predict adverse outcome and may aid the clinician in bedside decision making.Base deficit and serum lactate concentrations may be important prognostic indicators in preterm infants. We sought to (1) determine the relationship between day 1 serum lactate values and base deficit and (2) determine the relationship between day 1 biochemical parameters and adverse outcome in preterm infants <32 weeks. This was a retrospective study of all patients less than 32 weeks gestation admitted to neonatal intensive care unit over a 6-month period. All blood gases performed during the first 24 h post delivery were analysed. Adverse outcome was defined as death, severe (grade 3 or 4) intraventricular haemorrhage or periventricular leukomalaica on cranial ultrasonography. Patients were excluded if there was a known lethal malformation or cardiac defect. Seventy-two infants had a total of 473 lactate levels performed in the first 24 h. Mean (SD) gestational age was 29 (2.3) weeks, mean (SD) birth weight 1.28 (0.42) kg. Mean (SD) lactate values in first 6 h was 4.63 (3.69), at 12 h 3.08 (2.6), at 18 h 2.47 (2.68) and 2.08 (2.74) mmol/l at 24 h. There was a strong correlation between lactate values and base deficit values (R value 0.8, p < 0.01). Mean base deficit values at 6 h were 5.9 (4.5), at 12 h 3.8 (3.9), at 18 h 3.6 (3.1) and at 24 h 4.1 (3.8) mmol/l. A single lactate value greater than 5.6 mmol/l had a sensitivity of 100% and specificity of 85% of identifying adverse outcome. Persistently elevated or worsening lactates were associated with adverse outcome. There is a strong correlation between lactate values and base deficit on day 1 of life. Serial lactate measurements greater than 5.6 mmol/l predict adverse outcome and may aid the clinician in bedside decision making.