Survival of preterm and very low birth weight (VLBW) infants has steadily improved. However, the rates of mortality and morbidity among the very smallest infants are poorly characterized.Data from the California Perinatal Quality Care Collaborative for the years 2005 to 2012 were used to compare the mortality and morbidity of profoundly low birth weight (ProLBW, birth weight 300 to 500 g) and profoundly small for gestational age (ProSGA, <1st centile for weight-for-age) infants with very low birth weight (VLBW, birth weight 500 to 1500 g) and appropriate for gestational age (AGA, 5th to 95th centile for weight-for-age) infants, respectively.Data were available for 44 561 neonates of birth weight <1500 g. Of these, 1824 were ProLBW and 648 were ProSGA. ProLBW and ProSGA differed in their antenatal risk factors from the comparison groups and were less likely to receive antenatal steroids or to be delivered by cesarean section. Only 14% of ProSGA and 21% of ProLBW infants survived to hospital discharge, compared with >80% of AGA and VLBW infants. The largest increase in mortality in ProSGA and ProLBW infants occurred prior to 12 h of age, and most mortality happened in this time period. Survival of the ProLBW and ProSGA infants was positively associated with higher gestational age, receipt of antenatal steroids, cesarean section delivery and singleton birth.Survival of ProLBW and ProSGA infants is uncommon, and survival without substantial morbidity is rare. Survival is positively associated with receipt of antenatal steroids and cesarean delivery.