The neurodevelopmental outcome of children born after intracytoplasmic sperm injection (ICSI) is controversial. We compared the medical and developmental outcome of 34 singletons born after ICSI (20 males, 14 females; mean ages of 18mo and 40mo [SD 9mo]; range 2y 10mo–4y 8mo) with 39 case control studies (21 males, 18 females; mean ages of 18mo and 40mo [SD 4mo]; range 3y–4y 1mo). Each child was assessed physically and tested in three development domains (fine motor, gross motor, and language). Five children born after ICSI versus two control children (p=0.2) had major congenital anomalies (MaCAs). Four children born after ICSI versus no control children had severe MaCAs (p=0.04). These were defined as having a significant impact on development or causing chronic disease: Angelman syndrome (n=1), lissencephaly (n=1), Hanhart syndrome (n=1), and persistent hyperinsulinemic hypoglycaemia of infancy (n=1). Karyotyping in 23 children born after ICSI revealed no abnormalities. An imprinting defect was found in the child with Angelman syndrome. Results of developmental assessment were in all cases normal at the age of 18 months except for the three children with Angelman and Hanhart syndromes, and lissencephaly. At the second assessment, five more children born after ICSI and four control children showed abnormalities in one or more developmental domains. We conclude that there seems to be a higher frequency of severe major anomalies in children born after ICSI. An increased risk for imprinting defects cannot be excluded. If we exclude children with severe MaCAs, the incidence of an abnormal somatic or neurodevelopmental outcome in the fourth year of life in children born after ICSI is similar to that of spontaneously conceived children.