An investigation of the relationship between background knowledge and reading comprehension performance on standardized reading tests (the California STAR Test) was conducted with sixth, seventh, and eighth-grade ethnic minority children from low-income backgrounds (N = 68). Predictor variables examined included perceived background knowledge (overall and topic-specific), GPA, basic literacy skills, reading self-concept, race and ethnicity, language background, gender, and grade level. Research questions addressed participants' familiarity with topics discussed in STAR test reading passages and about the predictive nature of participant rankings and ratings of passages, as measured by the Topic Familiarity Ranking Measure and the Topic Familiarity Rating Scale. Results indicated that background knowledge of passage topics had a significant positive association (p <.05) with reading comprehension performance for 30% of the CST passages, for seventh and eighth-grade participants. Hierarchical regression analyses conducted on three of the passages showed that between 7% and 16% of the variance in reading comprehension performance was accounted for by background knowledge, as measured by the Topic Familiarity Rating Scale.