In 1999, computer-based test (CBT) administration was introduced for the United States Medical Licensing Examination (USMLE). Currently, all three Steps use ‘‘fixed forms’’: large numbers of tests are constructed to match detailed content and statistical specifications. However, use of sequential (adaptive) testing procedures is under consideration. When these procedures are used, examinees performing well are tested with progressively more difficult items; the reverse is true for examinees performing poorly. To the extent that the time required to respond to an item covaries with item difficulty, more proficient examinees may, as a result, be disadvantaged by adaptive testing procedures, and there is evidence in the literature that this occurs for some kinds of test material. The present study was undertaken as part of the effort to evaluate the desirability of introducing adaptive testing for USMLE. Specifically, the study was designed to gain a better understanding of the relationship between response times and item characteristics (word count, presence of pictures, difficulty), and the extent to which these relationships are influenced by an examinee’s proficiency and English-language background (native speaker vs English as a second language).