['We verified the effectiveness of training in endoscopic endonasal transsphenoidal surgery (eETSS) techniques using chicken eggs and a skull model.', 'We verified the area of eggshell removed by drilling when five residents and four experts used the chicken eggs and a skull model.', 'When residents performed drilling on 10 eggs, a mean (± standard deviation [SD]) area of 31.2 ± 17.5 mm2 was removed from the first egg, and 104.8 ± 3.3 mm2 from the tenth and final egg, representing an increase in area and a decrease in SD. The experts performed the same drilling operation on a single egg, and removed a mean area of 257± 31.7 mm2. These results demonstrated that skills improved as a result of this training, and suggested that this method was also capable of overcoming the initial individual differences in the amount of force applied and ability. An obvious difference between residents and experts was seen in the area removed (p = 0.00011); however, this was attributed to differences in endoscopic manipulation, rather than drilling skill.'] Does the chicken egg and skull model of endoscopic endonasal transsphenoidal surgery improve trainee drilling skills?