Objective: To determine whether the use of mixed micellar vitamin K improves the efficacy of the 3 × 2 mg oral vitamin K prophylaxis schedule. Design: Nationwide active surveillance for vitamin K deficiency bleeding (VKDB) complemented with two surveys on the use of the mixed micellar preparation in hospitals and by paediatricians. Setting and patients: Infants in Germany in 1997–2000. Intervention: Prophylaxis with three oral doses of 2 mg mixed micellar vitamin K. Main outcome measure: Confirmed VKDB between day 8 and week 12 and no condition requiring specific vitamin K supplementation known before the onset of bleeding. Results: Twenty nine reports met the case definition: seven had not received any vitamin K prophylaxis; for three, vitamin K prophylaxis was unknown; two had insufficient vitamin K prophylaxis for their age; 17 had been given the recommended doses. The mixed micellar preparation had been given to seven, other preparations to nine, and one had been given both. These cases did not differ with respect to the site of bleeding and cholestasis detected at bleeding. Estimates of the use of the mixed micellar preparation in birth hospitals and by paediatricians yielded 1 817 769 newborns exposed to the mixed micellar preparation and 1 320 926 newborns exposed to other preparations. The rate of late VKDB was 0.44/100 000 (95% confidence interval (CI) 0.19 to 0.87) in children given mixed micellar vitamin K compared with 0.76/100 000 (95% CI 0.36 to 1.39 ) in children given other preparations. Conclusion: Mixed micellar vitamin K did not significantly improve the efficacy of the 3 × 2 mg oral vitamin K prophylaxis schedule.