Background and Purpose-Agreement between physicians to define the likelihood of a transient ischemic attack (TIA) remains poor. Several studies have compared neurologists with nonneurologists, and neurologists among themselves, but not between fellowship-trained stroke neurologists. We investigated the diagnostic agreement in 55 patients with suspected TIA. Methods-The history and physical examination findings of 55 patients referred to the Stanford TIA clinic from the Stanford emergency room were blindly reviewed by 3 fellowship-trained stroke neurologists who had no knowledge of any test results or patient outcomes. Each patient's presentation was rated as to the likelihood that the presentation was consistent with TIA. We used 3 different scales (2-, 3-, and 4-point scales) to define TIA likelihood. We assessed global agreement between the raters and evaluated the biases related to individual raters and scale type. Results-The agreement between fellowship-trained stroke neurologists remained poor regardless of the rating system used and the statistical test used to measure it. Difference in rating bias among all raters was significant for each scale: Pϭ0.001, 0.012, and Ͻ0.001. In addition, for each reviewer, the rate of labeling an event an "unlikely TIA" progressively decreased with the number of points that composed the scale. Conclusions-TIA remains a highly subjective diagnosis, even among stroke subspecialists. The use of confirmatory testing beyond clinical judgment is needed to help solidify the diagnosis. Caution should be used when diagnosing an event as a possible TIA. (Stroke. 2010;41:1367-1370.)