The aims of this study were to assess the repeatability and reproducibility of transabdominal ultrasonography to assess intestinal wall thickness in adult Thoroughbred horses (n=8). Ultrasonographic cineloops were captured by one examiner from each horse for five consecutive days. During each examination at least three cineloops were obtained for five different intestinal tract locations. Measurements were performed by three separate observers to assess reproducibility and measured on three separate occasions by three observers to evaluate short-term repeatability. The repeatability of measurements from the duodenum (0.3±0.04 cm), jejunum (0.29±0.05 cm), ventral colon (0.37±0.01 cm), and cecum (0.42±0.03 cm) were good (P>0.291). The reproducibility of measurements from the duodenum, jejunum, and ventral colon were good (P>0.394). Reproducibility of measurement of the cecal wall was inadequate (P=0.01), although the maximum difference between observers was 0.07 cm. It was possible to image all areas on all days, with the exception of the duodenum, which could not be imaged in one horse, on 1 day. Equine intestinal wall measurements are therefore repeatable and reproducible with the exception of reproducibility of the measurements of cecal wall. Although an accepted clinical technique, measurement of cecal wall thickness from intestinal ultrasound images in a clinical setting must be interpreted with care.