Aim: To investigate the relation between echocardiographic parameters and 24-hour ambulatory blood pressure monitoring (ABPM) in normoalbuminuric pre-hypertensive adults with type 1 diabetes mellitus (T1DM) without clinical evidence of nephropathy or cardiovascular autonomic neuropathy. Methods: Adult patients who were diagnosed as T1DM and pre-hypertensive were categorized as dippers and non-dippers on the basis of 24-hour ambulatory blood pressure measurement and their echocardiographic parameters were compared. An oscillometric portable monitor took twenty-four hour blood pressure measurements automatically. A comprehensive echocardiographic evaluation was performed focusing on the left ventricular (LV) dimensions, LV mass index, relative wall thickness (RWT), left trial (LA) dimension and LV ejection fraction. Results: Of the 23 T1DM pre-hypertensive patients, 11 were categorized as dippers and 12 as nondippers. There were no differences between the dipper and the nondipper T1DM pre-hypertensive patients with respect to age, gender, body mass index, clinical and ABPM for average day-time systolic and diastolic blood pressure levels. Left ventricular (LV) internal diameters, LV septal and posterior wall thicknesses, LV ejection fraction (LVEF) were all similar in both groups. Left atrial diameter and LV mass index were found higher in the nondipper T1DM patients. There was no significant difference between two groups in terms of RWT although there was a trend for it to be higher in the nondipper group. Conclusion: Among prehypertensive T1DM patients evaluated by ambulatory BP monitoring, nondippers had higher LV mass index and left atrial dimensions compared with dippers. This may presage worse long term cardiovascular outcomes in nondippers.