OBJECTIVE: The objective of this study was to compare the McMaster’s Health Utilities Index-Mark III and the Euroqol-5D in a surgical breast cancer population. METHODS: Seventy-five surgical breast cancer patients participated in the study. The patients were given the Mark III version of the Health Utilities Index(HUI), and the Euroqol-5D(EQ) comprising both the classification system and the thermometer at the same visit, and the order of instrument administration was randomized. Information on the age of the patient, the cancer stage, and the number of comorbidities was obtained through chart review. RESULTS: The mean age of patients was 60 (sd=10.7). Ninety six percent of the patients were diagnosed with either stage I or II breast cancer. The majority of patients had up to 3 co-morbid conditions. The mean score on the HUI was 84.6 (sd=16.8). The mean on the EQ classification system was 87.4 (sd=13.6), while that on the EQ thermometer was 86.6 (sd=12.6). The correlation coefficient between scores on the HUI and the EQ classification system was 0.54, while that between the HUI and the EQ thermometer score was 0.66. Eight patients(10.6%) recorded the highest score on the HUI, thirty six patients(48%) on the EQ classification system, while 12 patients(16%) indicated ‘best imaginable health state’ on the EQ thermometer. The EQ classification system classified the patients into 15 health states, while 33 health states on the HUI classification system described the sample. CONCLUSION: The results of this study show that although both the HUI and the EQ classification systems are reliable measures of health status, they differ in terms of instrument sensitivity to disease severity.