OBJECTIVES: The objective of this project was to identify the treatment cost of malignant ascites from the Italian NHS perspective through a cost-analysis. Three reference centers in Italy contributed to this study during year 2012. METHODS: Three centers (Scientific Institute of Romagna for Cancer Studies and Treatment-I.R.S.T; Medical Oncology Unit of San Gerardo Hospital; Department of Gynecology of University Hospital Agostino Gemelli) were chosen due to the fact that they treat a representative sample of patients with malignant ascites in Italy. Each center was asked to complete three case report forms: the first identifying the costs for the pre-procedure diagnostic tests, the second identifying the specific procedure costs (paracentesis) and the third identifying the specific costs due to treatment of complications. All these reports had to be completed for the last 5 patients diagnosed with malignant ascites in order to prevent selection bias. A total cost for each patient was calculated by DRG analysis (standard cost – tariff). The DRG analysis assessed: day hospital, admission number, hospitalization, number of hospitalization days, principal diagnosis, main procedure/intervention, number of paracentesis procedures performed on the same patient with the same diagnosis, DRG type, DRG code, refund value for day hospital/ refund value for ordinary hospitalization. RESULTS: The analysis shows an average cost of € 1,464.42 per patient with malignant ascites using the DRG reimbursement rate (minimum value: €1,405.63; maximum value: €1,525.37). Analysis using DRG with complications resulted in a mean value of €1,524.84 (minimum value: €1,429.69; maximum value: €1,625.55). The key cost driver of malignant ascites treatment was the paracentesis procedure. CONCLUSIONS: The economic impact of paracenteses is high, especially when procedures must be repeated. The reduction in the number of paracenteses could reduce the costs while improving the QoL of the patients.