OBJECTIVE To investigate variables associated with myopic progression despite treatment in the Atropine in the Treatment of Myopia Study. METHODS Retrospective cohort study. METHODS Two hundred of 400 children were randomized to receive atropine 1% in 1 eye only in this institutional study. Children were followed up with cycloplegic autorefraction every 4 months over 2 years. Children whose myopia progressed by more than 0.5 diopter (D) in the atropine-treated eye at 1 year were classified as being progressors. RESULTS Among the 182 children still in the study at 1 year, 22 (12.1%) were classified as progressors. Univariate analysis suggested these children tended to be younger (8.5 ± 1.4 years vs 9.3 ± 1.5 years; P = .023), to have higher myopic spherical equivalent (SE) at baseline (-3.6 ± 1.3 D vs -2.8 ± 1.4 D; P = .015), and to have 2 myopic parents (77.3% vs 48.1%; P = .012). In nonprogressors, the myopia progression at 1 year was less in the atropine-treated eyes compared with the untreated fellow eye (+0.16 ± 0.37 D vs -0.73 ± 0.48 D; P < .001), but in progressors, progression was more similar between eyes (-0.92 ± 0.31 D vs -1.06 ± 0.44 D; P = .363). Regression analysis showed that the risk of being a progressor was 40% lower with each year of increased age, 43% lower for every 1.0 D less in myopia at baseline, and 59% lower for every 1.0 D less in myopic change in the untreated eyes over the first year. CONCLUSIONS Doctors and parents need to be aware that there is a small group of children (younger, with higher myopia, and greater tendency of myopic progression) who may still progress while receiving atropine treatment.