This study was principally concerned with the analysis of patterns of test taking and score change for examinees who repeated the TOEFL® test (Test of English as a Foreign Language™) in an International or Special Center Testing (I&SC) administration within 24 to 60 months after initial testing. Data for examinees who repeated the TOEFL test within 1 to 12 months following initial testing by institutions participating in the TOEFL Institutional Testing Program (INST) were also analyzed. In both the I&SC and INST samples, TOEFL test repeaters registered substantial average net gains in performance. Findings suggested that there may be differences among national-linguistic groups in typical rate of acquisition of proficiency in English. The magnitude of the average score changes found to be associated with test repetition for repeaters, combined with relatively strong differences among national-linguistic groups in both incidence of test repetition and mean score change, indicates that for purposes of summary reporting on TOEFL test performance (e.g., in defining basic reference groups), it is important to specify the test-repetition status of the groups of examinees involved.