Abstract: Anaesthesia is important in handling large river eels during procedures such as measuring, tagging and surgery. Therefore, the use of eugenol as an anaesthetic for the Australian longfinned eel, Anguilla reinhardtii (Steindachner) was investigated with a range of concentrations (10-120 mg/L). 20-120 mg/L of eugenol was found to be safe and effective (P <0.05), which could induce anaesthesia in less than 10 min, and recover after anaesthesia also in less than 10 min with a recovery rate of 100%. The difference of induction times and recovery times among 40, 60, 80 and 100 mg/L was not statistically significant, but with and among other groups was significant (P <0.05). Interestingly, average induction times did not always drop as the concentration increased. The induction time decreased from 312.88 s to 252.25 s when the concentration increased from 20 mg/L to 30 mg/L, while increased greatly to 582.00 s when attained 40 mg/L. Between 40-120 mg/L, induction times were inversely correlated with concentrations (r =-0.84, P <0.05), and dropped again in general along with the increase of concentration. Mean recovery time was the shortest for 20 and 30 mg/L, and shorter for 120 mg/L, and showed correlations of a certain degree both with anaesthetic concentration and induction time (r = 0.52, P <0.05). In conclusion, eugenol is a safe and effective anaesthetic for the Australian longfinned eel. 20-30 mg/L of anaesthetic concentration which can induce anaesthesia in 4-5 min in average and recover after anaesthesia in 4-7 min is recommended.