We studied the efficacy of neostigmine and edrophonium to reverse an atracurium-induced 90% neuromuscular block in 80 paediatric patients anaesthetized with thiopentone, fentanyl and nitrous oxide. The patients were divided into five age groups: 0-2 months, 3-11 months, 2-5 years, 6-10 years, and 11-15 years. At the end of surgery, the neuromuscular block was randomly antagonized with either neostigmine 50 mu g kg(-1) with atropine 20 mu g kg(-1) or with edrophonium 1 mg kg(-1) with atropine 10 mu g kg(-1). In general, the first EMG response and cain-of-four (TOF) ratio recovered fastest in the youngest age groups following either reversal agent (P<0.05). However, in each age group edrophonium had a faster onset of effect than neostigmine (P<0.05) even though a greater TOF-ratio was finally reached with neostigmine. The effects of neostigmine were less variable and more predictable than those of edrophonium. Therefore, we recommend the use of neostigmine for routine paediatric practice.