PURPOSE:LMA® ProSeal™ (pLMA) has been used as an alternative to tracheal tubes. It is unclear how many cases are required to achieve proficiency in performing pLMA insertion among novice residents. Therefore, we analyzed the learning curve of pLMA insertion using a cumulative sum (CUSUM) chart and assessed the effects of learning. METHODS:In this single-center, prospective, observational study, we included 15 novice residents. Staff anesthesiologists recorded success or failure; insertion time; and incidences of bleeding or reflex including cough, hiccups, and limb movement. A successful pLMA insertion was defined as effective ventilation within two attempts with an insertion time of ≤ 120 s. Regarding CUSUM, we set acceptable and unacceptable failure rates as 20% and 40%, respectively. Further, α and β errors were designated as 0.1. We stratified the number of cases encountered by each resident into four groups of 10 cases each (1-10, 11-20, 21-30, and ≥ 31 cases) and evaluated the effects of learning. RESULTS:Each resident encountered 44 ± 5 (mean ± SD) cases of pLMA insertion, and 14/15 achieved proficiency in performing pLMA insertion after 20 ± 8 cases. Success rate (76%, 86%, 91%, and 93%; P < 0.001) and insertion time (45 s, 35 s, 31 s, and 26 s; P < 0.001) significantly improved with increased experience; however, incidences of bleeding (16%, 10%, 8%, and 10%; P = 0.124) and reflex (5%, 3%, 3%, and 3%; P = 0.54) remained unchanged. CONCLUSION:Experience with 20 ± 8 cases is needed to achieve proficiency in performing pLMA insertion for novice residents in a tertiary teaching hospital.