A meta-analysis using Hierarchical Linear Modeling (HLM) was conducted to examine the effects of test accommodations on the test performance of English language learners (ELLs). The results indicated that test accommodations improve ELLs' test performance by about 0.157 standard deviations--a relatively small but statistically significant increase. Once the potential predictors that may have contributed to the variance of the effect sizes across studies had been accounted for, only English proficiency was found to be significant. Further, the results indicated that ELLs with a low level of English proficiency benefited much more from test accommodations than did those with a high level of English proficiency. Little difference was observed in regard to other factors such as students' ethnicity, students' grade level, or the subject for which they were being examined. Although previous studies have suggested that linguistic simplification may be more effective than other methods, results from this meta-analysis offered no support for that suggestion. (Contains 3 tables and 2 footnotes.)