Quality of life (QOL) is increasingly assessed in cancer patients. In this article, the authors examined the psychometric performance of a commonly used QOL questionnaire, the Quality of Life Questionnaire--Cancer 30 (QLQ-C30; N. K. Aaronson et al., 1993), in multiethnic cancer patients. Content validation studies in patients and clinicians identified possible new items. Multiple-group confirmatory factor analysis supported equivalent structure across ethnic groups (Caucasians and Asian/Pacific Islanders [APIs]). A higher order QOL factor appeared to directly affect functioning scales and symptom count. Exploratory factor analysis examined effects of new items. Ten factors were extracted, 6 consistent with the original instrument and 4 reflecting potentially new aspects of QOL: Positive Social Support, Coping, Existential Well-Being, and Sexuality/Intimacy. The QLQ-C30 appears appropriate for use in API cancer patients. Further work needs to ensure that it includes all important domains.