OBJECTIVE To study if severe hyperbilirubinemia in infants with no or minor neurologic symptoms in the neonatal period affects children's development at the age of 1 to 5 years. METHODS Controlled descriptive follow-up study of a national cohort of Danish children. The exposed group consisted of all live-born infants in Denmark from 2004 to 2007 with a gestational age ≥ 35 weeks and severe hyperbilirubinemia in the neonatal period, defined as at least 1 measure of total serum bilirubin level ≥ 25 mg/dL during the first 3 weeks of life. The exposed group of 206 children was matched with a control group of 208 children. The Ages and Stages Questionnaire (ASQ), a method of evaluating the child's development, was filled in by parents. Main outcome measure was effect size of ASQ total score. Statistical analyses comprised a matched analysis of 102 pairs and a nonmatched regression analysis of all participants. RESULTS The response rate was 79% (n = 162 of 206) in the study group and 70% (n = 146 of 208) in the control group. Neither the matched nor the nonmatched analysis showed any statistically significant differences between the groups; the effect size of the total score was 0.04 (-0.24 to 0.32) and -0.04 (-0.26 to 0.19), respectively. CONCLUSIONS Using the parent-completed ASQ, we found no evidence of developmental delay in children aged between 1 and 5 years with severe neonatal hyperbilirubinemia compared with a matched control group.