To evaluate the efficacy and safety of topical atropine, a nonselective muscarinic antagonist, in slowing the progression of myopia and ocular axial elongation in Asian children. Parallel-group, placebo-controlled, randomized, double-masked study. Four hundred children aged 6 to 12 years with refractive error of spherical equivalent -1.00 to -6.00 diopters (D) and astigmatism of -1.50 D or less. Participants were assigned with equal probability to receive either 1% atropine or vehicle eye drops once nightly for 2 years. Only 1 eye of each subject was chosen through randomization for treatment. The main efficacy outcome measures were change in spherical equivalent refraction as measured by cycloplegic autorefraction and change in ocular axial length as measured by ultrasonography. The primary safety outcome measure was the occurrence of adverse events. Three hundred forty-six (86.5%) children completed the 2-year study. After 2 years, the mean progression of myopia and of axial elongation in the placebo-treated control eyes was -1.20+/-0.69 D and 0.38+/-0.38 mm, respectively. In the atropine-treated eyes, myopia progression was only -0.28+/-0.92 D, whereas the axial length remained essentially unchanged compared with baseline (-0.02+/-0.35 mm). The differences in myopia progression and axial elongation between the 2 groups were -0.92 D (95% confidence interval, -1.10 to -0.77 D; P<0.001) and 0.40 mm (95% confidence interval, 0.35-0.45 mm; P<0.001), respectively. No serious adverse events related to atropine were reported. Topical atropine was well tolerated and effective in slowing the progression of low and moderate myopia and ocular axial elongation in Asian children.