Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are considered the standard of care for patients with peritoneal dissemination of appendiceal cancer and are increasingly being evaluated for use in patients with carcinomatosis from colon cancer. Mitomycin C (MMC) is one of the most frequently used HIPEC agents in the management of peritoneal-based gastrointestinal malignancies. This study analyzes the incidence and risk factors for developing neutropenia following MMC-HIPEC combined with CRS. All patients undergoing CRS and MMC-HIPEC for appendiceal cancer between January 1993 and October 2006 were retrospectively reviewed. Logistic regression was used to identify risk factors for the development of neutropenia, defined as an absolute neutrophil count (ANC) <1,000/mm(3). One hundred and twenty MMC-HIPEC were performed in 117 patients with appendiceal cancer. The incidence of neutropenia was 39%. Neutropenia occurred in 57.6% of female and 21.3% of male patients (p < 0.0001). Female gender and MMC dose per body surface area (BSA) were independent risk factors for neutropenia on multivariable logistic regression [odds ratio (OR) of neutropenia in females = 3.58 (95% confidence interval, CI: 1.52, 8.43); OR for 5 unit (mg/m(2)) increase in MMC dose per BSA = 3.37 (95% CI: 1.72, 6.63)]. Neutropenia did not increase the risk of mortality, postoperative infection or length of hospital stay. Neutropenia is a frequent complication associated with MMC-HIPEC. Female sex and MMC dose per BSA are independent risk factors for neutropenia. These differences must be considered in the management of patients undergoing MMC-HIPEC to minimize the toxicity of the procedure.