The reported ranges of aortic root (AR) diameters are limited by small sample size, different measurement sites, and heterogeneous cohorts. The aim of this study was to explore the full spectrum of AR diameters by 2-dimensional transthoracic color Doppler echocardiography (TTE) in a large cohort of healthy adults. From June 2007 to December 2013, a total of 1,043 Caucasian healthy volunteers (mean age 44.7 ± 15.9 years, range 16 to 92 years, 503 men [48%]) underwent comprehensive TTE. TTE measurements of the AR were made at end-diastole in parasternal long-axis views at 4 levels: (1) annulus, (2) sinuses of Valsalva, (3) sinotubular junction, and (4) proximal ascending aorta. The absolute aortic diameters were significantly greater in men than in women at all levels, whereas body surface area–indexed aortic diameters were greater in women (p = 0.0001). No significant gender differences were registered for sinuses of Valsalva and sinotubular junction to annulus diameter ratios (p = 0.9), whereas ascending aorta to annulus diameter ratio was higher in women (p = 0.0001). There was a straight correlation between aortic diameters (absolute and indexed values), their ratios, and age in both genders (p = 0.0001). In conclusion, we provide the full range of AR diameters by TTE. Knowledge of upper physiological limits of aortic dimensions is mandatory to detect aorta dilatation, follow up the disease over time, and plan appropriate therapeutic interventions.