The purpose of this study was to conduct a comparative cost analysis of myringotomy with insertion of ventilation tube (MVT) for children performed at two regional paediatric centres: The Hospital for Sick Children, and the British Columbia Children's Hospital. A comparative cost analysis was conducted between the Hospital for Sick Children (HSC), Toronto, and the British Columbia Children's Hospital (BCCH), Vancouver. The cost analysis was performed from a health system perspective using a treatment protocol developed through a review of the literature and input from staff from each of the study hospitals. MVT cost estimates were derived, including direct treatment costs and overhead costs. Total costs per MVT case (in 1994 Canadian dollars: Cdn$ 1.00 approximately US$ 0.75) varied from $390.81 at BCCH to $455.63 at HSC. Regional variations in physician costs accounted for almost 70% of the difference in MVT case costs. The distribution of nonphysician MVT case costs were similar in each study hospital, with direct (nonphysician) surgical costs, preoperative assessment and recovery room costs, and administration accounting for 30%, 26%, and 44% of total nonphysician costs, respectively. This study identified the magnitude and determinants of regional variations in the cost of MVT surgery. Such cost estimates serve as an important (but not the sole) ingredient in service cost-effectiveness deliberations and in the formulation of evidence-based care when health care resources are scarce.