Background: There have been few studies investigating advanced gastric cancer with peritoneal involvement and ascites, showing poor survival in these patients. Researchers from Japan have shown that chemotherapy with IPP and Oral S-1 (tegafur/gimeracil/oteracil) is active in these patients. These results have been achieved in a different genetic pool (Japanese population) compared with Australia, using regimens that are not available here. We have designed this phase I trial to investigate the Maximum Tolerated Dose (MDT) of IPP in combination with a standard chemotherapy combination (C+X) in these patients. Methods: This is an open-label, single centre, phase I trial with 3+3 expanded cohort design. Patients will have an IP catheter placed surgically after trial enrolment. Study was approved by the relevant ethics committee. Chemotherapy: maximum of six 21-day cycles of: X (PO, 1000 mg/m2 BD days 1-14) + C (IV 80mg/m2 day 1) + IPP (day 1 and 8) with the following doses: Cohort-1: 10 mg/m2, Cohort-2: 20 mg/m2 and Cohort-3: 30 mg/m2. Important inclusion criteria: age ≥ 18 years, signed written informed consent, HER-2 non-amplified gastric adenocarcinoma with biopsy or cytology showing peritoneal involvement and/or ascites, adequate organ function and signed consent. Important exclusion criteria: history of another malignancy within 5 years, life expectancy < 3months, peripheral neuropathy, recent ( < 4 weeks) abdominal or pelvic radiation treatment, significant intra-abdominal adhesions or active intra-abdominal sepsis. Cohorts 1 and 2 have been completed. Enrolment to cohort-3 is beginning in October 2017. Clinical trial information: ACTRN12614001063606.