OBJECTIVE To investigate the visual acuity development as measured by Landolt C and Tumbling E charts ("C chart" and "E chart") in preschool children. METHODS Visual acuity measurements of healthy children ages 3-6 years who had been evaluated with the use of E charts (during kindergarten screening) and C charts (in a hospital setting) from 2005 to 2007 were studied. Inclusion criteria were hyperopia <4.5 D, myopia <3.0 D, astigmatism <2.0 D, and anisometropia <2.0 D. The best-corrected visual acuity (BCVA) in each group was analyzed. RESULTS There were 821 children in the E chart group and 212 in the C chart group (mean age, 5 years). The mean BCVA improved from between age 3-4 years and age 5-6 years in both groups (P < 0.001). Children in the C chart group had significantly greater astigmatism compared with those in the E chart group (0.66 D ± 0.47 vs 0.28 D ± 0.39; P < 0.001). The BCVA obtained by E chart was greater than that obtained by C chart at age 3-4 years (logMAR 0.0246 ± 0.0646 vs 0.1158 ± 0.1462, P < 0.001), but not at age 5-6 years. CONCLUSIONS When children reach 5-6 years of age, visual acuity values obtained by C and E charts approach those observed in adults. In younger patients, the E chart obtains a greater visual acuity score than the C chart. Thus, thresholds for normal visual acuity in preschool children ages 3-6 years should be both age specific and test specific.