Vitamin K prophylaxis is recommended to prevent the hazard of haemorrhage caused by vitamin K deficiency in newborns. The present Dutch guideline recommends 1 mg of vitamin K(1) orally at birth, followed by a daily dose of 25 microg of vitamin K(1) from 1 to 13 weeks of age for breastfed infants. Since the introduction of this prophylaxis, the incidence of vitamin K deficiency bleeding (VKDB) has decreased; however, late VKDB is still reported. From 1 January to 31 December 2005, a nationwide active surveillance was performed by the Netherlands Paediatric Surveillance Unit (NSCK) to study the current incidence and aetiology of late VKDB in infants. Six cases could be validated as late VKDB: all were breastfed, one fatal idiopathic intracranial haemorrhage at the age of 5 weeks and five bleedings secondary to an underlying cholestatic liver disease between the age of 3 and 7 weeks. The total incidence of late VKDB and idiopathic late VKDB was calculated to be 3.2 (95% CI: 1.2-6.9) and 0.5 (95% CI: 0-2.9) per 100,000 live births, respectively. With the current Dutch guideline, idiopathic late VKDB is rare but late VKDB secondary to cholestasis still occurs in breastfed infants. Doubling the daily dose of vitamin K(1) to 50 microg, as is comparable to formula-feeding, may possibly prevent VKDB in this group. Further research, however, is needed to prove this hypothesis.