Rationale: Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS + HIPEC) and systemic therapy are increasingly used for the treatment of peritoneal metastases of colorectal cancer (PMCRC). Subsequently, combined treatment strategies have been introduced, with the use of perioperative systemic therapy, either neoadjuvant or adjuvant, as adjunct to CRS + HIPEC. However, current literature on perioperative systemic therapy as adjunct to CRS + HIPEC is based on observational studies of low methodological quality, thereby leading to worldwide controversy on its benefit. A neoadjuvant treatment strategy that potentially downstages intraperitoneal tumour load, limits extensiveness of CRS, and predicts the biological behaviour of the tumour, appears to be of potential benefit. In patients who proved to respond to neoadjuvant treatment with sufficiently good clinical condition, adjuvant systemic therapy in the same regimen may be of value by further treating micro-metastases.