A one year, retrospective audit of intermittent vancomycin therapy within the Neonatal Unit at the Royal Hospital for Sick Children, Glasgow, found that only 33% of 984 vancomycin trough levels were within the British National Formulary for children (BNFc) target range of 10–15 mg/l and 25% were <10 mg/l. A detailed, prospective review of 20 courses (15 patients) over one month, while using the same dosing guidelines, highlighted that only 23 of 50 concentration measurements (46%) were within the target range and 20% were <10 mg/l, even though the initial doses used (table 1) were higher than those recommended by the BNFc. Dose adjustments were common and up to 80 mg/kg/day was often required for older infants. Appropriate interpretation of concentration results was compromised