OBJECTIVES: Although utility-based algorithms have been developed for the Functional Assessment of Cancer Therapy (FACT), their properties are not well-known compared to more widely used utility measures like the EQ-5D.  The objective of this study was to compare the properties and relationships between EQ-5D and FACT-based health utility scores in cancer patients.   METHODS: A retrospective analysis was conducted on cross-sectional data collected from 534 cancer patients who completed both FACT-G and EQ-5D.  Properties of scores from 3 FACT-based and 2 EQ-5D based algorithms were examined.  Known groups comparisons were based on physician and patient-rated ECOG performance status.  Relative efficiency (RE) of the utility algorithms was examined using ratios of F-statistics.      RESULTS: Mean scores for the overall cohort were lowest using Kind and Macran’s FACT UK societal (0.55, SD 0.09), followed by Dolan’s EQ-5D UK societal (0.72, SD 0.23), Cheung et al.’s FACT mapped to EQ-5D (0.74, SD 0.11), Shaw et al.’s EQ-5D US societal (0.79, SD 0.15), and highest using Dobrez et al’s FACT US patient algorithm (0.83, SD 0.08).  When stratified by ECOG status, the largest differences in mean scores were generally observed for EQ-5D UK societal scores and smallest for the FACT-based US patient scores; however, FACT UK societal scores had twice the statistical efficiency of the other algorithms.  CONCLUSIONS: We found important differences in utilities scores estimated by each algorithm.  The FACT-based algorithms tended to underestimate the QALY benefit compared to the EQ-5D, and appeared to driven by a more limited range of scale.