Primary Nocturnal Enuresis (PNE), or nighttime bedwetting, is the second most common chronic ailment in childhood. Fifteen to 20% of 5 year-olds wet at least monthly. It has been estimated that up to 10% of children with PNE will remain enuretic throughout their lifetime if untreated. OBJECTIVE: This model was developed to determine the cost effectiveness of therapies for PNE. METHODS: A decision tree model was developed on software designed by Treeage Software Inc. to access the cost-effective treatment of PNE. The model assumed 6 months of initial treatment for 100 patients in each group. If the initial treatment failed or the patient relapsed, they were retreated with an alternative therapy. Probabilities used in the model to determine patient responses, relapses, and complication rates were obtained from published clinical trials. The model includes direct cost including drug acquisition, physician consultation, intensive behavioral management (IBM), relapses, and complications. Probabilities and direct cost data for vasopressin (DDAVP), IBM, minor or serious adverse events (AE), and relapses were included in the model. Indirect cost included cost of disposable and nondisposable diapers, excess wear on bedclothes and sheets, washing and drying and the caregiver's time. The cost of these assumed 5 wet nights per week. Effectiveness was determined when there was a significant increase in dry patient nights. RESULTS: The cost effectiveness ratio (total cost¸effectiveness) for IBM is $14,607 versus $17,608 and $19,644 respectively for IBM, oral and inhaled DDAVP for a complete treatment cycle. One-way sensitivity analysis did not substantially alter the results. CONCLUSION: The model identifies Intensive Behavioral Management as cost effective treatment of Primary Nocturnal Enuresis.