PURPOSE: To investigate the usefulness of dynamic MR imaging in the diagnosis of pituitary microadenomas. MATERIALS AND METHODS: Dynamic MR imaging was performed in 31 patients with suspicious pituitary microadenoma. The MR examination was performed on a 2.0T or 1.5T superconductive MR unit using spin echo(SE) technique with arepetition time of 200m sec, echo time of 15 m sec, 128 x 256 matrix and one excitation. Actual sampling time perimage was 26 seconds. The field of view was 25cm and a section thickness of 3mm with 2mm gap was chosen. After arapid hand injection(2-3ml/sec) of Gd-DTPA(0.1 mmol/kg of body weight), dynamic coronal plane MR images were obtained every 20-30 seconds for 3-5 minutes. Between never and ten serial images were usually obtained. After dynamic MR imaging, routine SE T1-weighted images(T1WI) were obtained in the same plane as dynamic images, and detection rates of pituitary microadenoma using dynamic MR imaging and using routine enhanced T1WI, were retrospectively compared. RESULTS: On early dynamic images(30|90 seconds), 23 of 31 adenomas(74.2%) were well visualized, with a clear border ; of particular note is the fact that 11 of the 31 were well visualized at 30-second dynamic image. On late dynamic images(120-180 seconds), six microadeomas(19.4%) were well-visualized and; two(6.5%) were well-visualized throughout on all dynamic images. Meanwhile, 12 of 31 microadenomas(38.7%) were well-visualized on routine Gd-DTPA enhanced T1WI. CONCLUSION: Dynamic MR imaging with Gd-DTPA bolus injection was the most useful technique for the detection of pituitary microadenomas, especially on early-phase dynamic images.