Probit analysis was used to predict the median effective concentration (EC50) and the 95% effective concentration (EC95) values of levobupivacaine for caudal analgesia in children at equal volumes of injectate. Sixty children scheduled for inguinal herniorrhaphy were recruited. Anaesthesia was induced with sevofurane and nitrous oxide. Then caudal block (total volume of local anaesthetic 1 ml.kg−1) was performed. Patients randomly received one of six concentrations (0.08%, 0.10%, 0.12%, 0.14%, 0.16% or 0.18%) of levobupivacaine. Thereafter, inhalational anaesthetics were discontinued and intravenous midazolam 0.1 mg.kg−1 was administered to maintain sedation. The effective caudal analgesia was defined as an absence of gross movements and a haemodynamic (heart rate or blood pressure) reaction < 20% compared with baseline in response to surgical incision. Our data indicated that the EC50 and EC95 values of levobupivacaine for caudal analgesia were 0.109% (95% confidence intervals 0.098–0.120%) and 0.151% (95% confidence intervals 0.135–0.193%) when using the same volume (1 ml.kg−1), respectively.