OBJECTIVES: To describe treatment patterns, resource use and associated costs for cancer patients with malignant ascites (MA) receiving paracentesis in Germany. METHODS: The study was conducted as an observational, multicentre, prevalence-based cohort study. Inclusion criteria were: age ≥18 years, diagnosis of ovarian or gastrointestinal carcinoma (CA) with MA, paracentesis as treatment option for MA at the time of enrolment. Resource consumption data were collected by chart review and patient questionnaire covering the time period from the first paracentesis documented in the study until ascites diagnosis retrospectively and subsequent paracenteses prospectively. Direct medical costs were analysed from third party payers’ (TPP) and patients’ perspective. RESULTS: A total of 29 patients (38% male) with a mean age of 65±9 years were enrolled at 11 centers (6 hospitals, 5 office-based practices) between July 2008 and August 2009. Seven patients had ovarian CA (24%), 5 gastric CA (17%) and 17 other gastrointestinal CAs (59%). A total of 101 paracenteses were documented for all patients. From ascites diagnosis to death patients received on average 4.6 paracenteses. Mean time between two paracenteses was 11.9±12.3 days. Data from 42 paracenteses were eligible for resource and cost analysis. Diuretics were applied in 57% of paracentesis units and human albumin in 29%. Intraperitoneal chemotherapy was applied rarely (5%). From TPPs’ perspective mean total costs per paracentesis unit amounted to €1,064±1,453, from patients’ perspective €17±46. Direct medical costs per paracentesis unit varied from €671±1,070 at office-based practices to €2.742±1.535 at hospitals (inpatient treatment). CONCLUSIONS: This is the first comprehensive study evaluating the burden of MA in cancer patients undergoing paracentesis in Germany. Our findings indicate that the costs for paracentesis range around €670 to €2700 depending on health care setting. Our results might serve as a basis for further research on the economic implication of malignant ascites.