Goals of work: To determine the relative validity of the Malnutrition Screening Tool (MST) compared with a full nutrition assessment by the scored Patient Generated-Subjective Global Assessment (PG-SGA) and to assess MST inter-rater reliability in patients receiving chemotherapy. Patients and methods: An observational, cross-sectional study was conducted at an Australian public hospital in 50 oncology outpatients receiving chemotherapy. Inter-rater reliability was assessed in a subsample of 20 patients. Main results: According to PG-SGA global rating, the prevalence of malnutrition was 26%. The MST was a strong predictor of nutritional risk relative to the PG-SGA (100% sensitivity, 92% specificity, 0.8 positive predictive value, 1.0 negative predictive value). MST inter-rater reliability was acceptable with agreement by administration staff/nursing staff/patient and the dietitian in 18/20 cases (kappa=0.83; p0.001). Conclusion: The MST has acceptable relative validity, inter-rater reliability, sensitivity, and specificity to identify chemotherapy outpatients at risk of malnutrition and, hence, is an acceptable nutrition screening tool in this patient population.