OBJECTIVES: The UCLA Prostate Cancer Index (UCLA-PCI) is a disease specific Health-related Quality of Life (HRQOL) measure used in early stage prostate cancer patients. We examined the UCLA-PCI's measurement properties in this study. METHODS: We systematically identified all published papers citing the original publication using the Science Citation Index. For completeness, we also searched the PubMed and Ovid databases from 1995 to the present. We analyzed all English articles reporting measurement properties of the UCLA-PCI. RESULTS: We identified 224 papers. Seventy-seven of these papers reported results using the UCLA-PCI in either cross-sectional designs (43) or in longitudinal analyses (34). The UCLA-PCI exhibited high reliability (intraclass correlation coefficients ranged from 0.66 to 0.97). The UCLA-PCI also had good face and content validity, as demonstrated by the number of studies that incorporated the instrument and by its translation into five other languages. The construct validity of the UCLA-PCI's functioning domains has been demonstrated with correlations of 0.42 to 0.88 when compared with other relevant disease-specific HRQOL measures; however further study comparing the UCLA-PCI to other disease-specific HRQOL measures (FACT-P, EORTC-P, IPSS) may be warranted. Although this instrument has been used in many longitudinal research designs, its evaluative validity only was assessed in one study (effect sizes ranged from 0.77 to 1.51). The responsiveness of the UCLA-PCI to HRQOL changes has been shown in many studies usually by comparing changes in the study population with the UCLA-PCI values of older men without prostate cancer (reported in 1999). To maximize interpretability of each domain, both anchor and distributional techniques should be utilized to determine what changes the patient may perceive as minimally important differences. CONCLUSIONS: Although the UCLA-PCI has been shown to be reliable and valid, we encourage further research establishing its interpretability and expanding its validity through its assessment in clinical trials.