© American Roentgen Ray Society. OBJECTIVE. The purpose of this study was to estimate the prevalence of reported nearmiss wrong-patient events in radiology at two large academic hospitals and its relation to imaging modality, clinical setting, and time of occurrence. MATERIALS AND METHODS. An institutional imaging report database was searched for reports between January 1, 2009, and May 30, 2013, that contained the phrases "incorrect patient" or "wrong patient." These imaging reports were categorized into either mislabeled or misidentified patient or wrong dictation or report events. The mislabeling-misidentification events involved patients whose images were incorrectly placed in another patient's folder. In wrong dictation or report events, a patient's images were placed in the correct imaging folder, but another patient's images were used in error for dictation of the report. The time to detect each of these events was also evaluated. RESULTS. Overall, 67 eligible reports were identified among 1,717,713 examinations performed during the study period. The estimated event rate was 4 per 100,000 examinations (mislabeling-misidentification, 52%; wrong dictation, 48%). The monthly mean of mislabeling- misidentification events was 0.7 (SD, 0.9) and of wrong dictation events was 0.6 (SD, 0.7). The median time for mislabeling-misidentification reports to be identified was 22 hours and for wrong dictation reports was 0 hours. Portable chest radiography was the modality involved in 69% (24/35) of reported mislabeling-misidentification and 44% (14/32) of wrong dictation events (p = 0.08); 43% (15/35) of mislabeling-misidentification and 28% (9/32) of wrong dictation events occurred during off hours; 63% (22/35) of mislabeling-misidentification and 56% (18/32) of wrong dictation events occurred in the inpatient setting. CONCLUSION. Despite use of the dual-identifier technique mandated by The Joint Commission, the number of near-miss mislabeled patient events for imaging tests and the delay in awareness of these events were substantial, especially for radiography.