Umbilical cord blood gas values and morbidity and mortality were correlated in 191 very low birth weight (VLBW) infants (500-1500 g). The mean umbilical arterial pH and base excess differed significantly between survivors and non-survivors. The presence of at least moderate acidosis (arterial pH 7.15 or lower) was related significantly to mortality, particularly in infants younger than 26 weeks. The mean cord blood gas values did not predict the presence or severity of hyaline membrane disease or intraventricular hemorrhage, but Apgar scores did. Bronchopulmonary dysplasia, neurologic sequelae, necrotizing enterocolitis, and sepsis also did not correlate with mean cord gas values, but neither did Apgar scores. Furthermore, the severity and type of acidosis did not relate to morbidity. Combining cord blood gases and Apgar scores did not help predict morbidity, which was not surprising because cord pH values correlated poorly with Apgar scores (all r values less than or equal to 0.26). We urge caution in interpreting cord gases as predictors of morbidity in the VLBW infant.