BACKGROUND:: Accurate data on the optimal chloride intake in premature infants are scarce. OBJECTIVE:: To describe chloride (Cl) intakes in the first 10 days (D) of life and to assess the relationships between high Cl intakes and corrected serum chloride level or markers of severe acidosis in infants less than 28 weeks gestation. METHODS:: Retrospective cohort study including all infants < 28 weeks admitted to the neonatal intensive care unit over a 3-year period and cared for from birth until D10 or more. RESULTS:: Fifty-six infants were included. Cumulative total Cl intakes reached (mean +/- SD) 9.6 +/- 3.7 mmol/kg at day 3 and 49.2 +/- 13.5 mmol/kg at D10. Inadvertent intakes (from intravenous fluids other than parenteral nutrition) represented on average 70% of total Cl intakes in the first 3 days. Difference between Cl and sodium intakes reached (mean +/- SD) 7.8 +/- 4.8 mmol/kg at D10 and mainly originated from parenteral nutrition. By multivariate analysis, cumulative Cl intake > 10 mmol/kg during the first 3 days was an independent risk factor of base excess <-10 mmol/l. Cumulative Cl intake > 45 mmol/kg during the first 10 days was an independent risk factor of corrected chloremia > 115 mmol/l and of base excess <-10 mmol/l. CONCLUSIONS:: Cumulative Cl intake over 10 mmol/kg during the first 3 days (i.e. 3.3 mmol/kg/d on average) and over 45 mmol/kg during the first 10 days (i.e. 4.5 mmol/kg/d on average) may have unwanted metabolic consequences and should be avoided. Imbalance between electrolytes provided by the parenteral nutrition solution need to be detected and corrected.