SUMMARYThis paper aims (a) to determine whether variations in the hospital costs of appendectomy in EU member states are larger within individual countries or between different countries and (b) to explore causes for variations in costs between hospitals and countries. To do so, hospitalisation costs and reimbursement rates for appendectomy were obtained from 54 hospitals in nine European member states based on 1786 cases using a standardised methodology. Regression analysis was performed using hospital characteristics, treatment characteristics, and purchasing power parities (PPP) as explanatory variables in a multilevel framework. The within-country standard error was estimated to h294 (27%), whereas the between-country standard error was h796 (73%). Excluding hospitals in Spain, Hungary, and Poland, which had significantly lower costs than hospitals in the other countries in our analysis, the within-country standard error was h331 (57%) and the between-country standard error dropped to h248 (43%). Regression results show that the treatment decision for open surgery was associated with significantly lower costs, whereas a greater number of beds and a higher staff per bed ratio were associated with significantly higher costs. PPP explained a major part of the between-country variance.