AbstractObjectivesThe objective of this study is to determine the optimal timing for device‐based infant circumcision under topical anaesthesia.Subjects/patientsWe include infants aged 1–60 days who were enrolled in a field study of the no‐flip ShangRing device at four hospitals in the Rakai region of south‐central Uganda, between 5 February 2020 and 27 October 2020.MethodsTwo hundred infants, aged 0–60 days, were enrolled, and EMLA cream was applied on the foreskin and entire penile shaft. The anaesthetic effect was assessed every 5 min by gentle application of artery forceps at the tip of the foreskin, starting at 10 min post‐application until 60 min, the recommended time to start circumcision. The response was measured using the Neonatal Infant Pain Scale (NIPS). We determined the onset and duration of anaesthesia (defined as <20% of infants with NIPS score >4) and maximum anaesthesia (defined as <20% of infants with NIPS score >2).ResultsOverall, NIPS scores decreased to a minimum and reversed before the recommended 60 min. Baseline response varied with age, with minimal response among infants aged 40 days. Overall, anaesthesia was achieved after at least 25 min and lasted 20–30 min. Maximum anaesthesia was achieved after at least 30 min (except among those aged >45 days where it was not achieved) and lasted up to 10 min.ConclusionThe optimal timing for maximum topical anaesthesia occurred before the recommended 60 min of waiting time. A shorter waiting time and speed may be efficient for mass device‐based circumcision.