['To characterize seasonal variation in the myopic progression of Chinese children.', 'Myopia progression data are presented for a total of 85 Chinese children, aged 6 to 12 years, with baseline myopia of -0.75 D to -3.50 D sphere and astigmatism ≤-1.50 D, who wore traditional single-vision spectacles in two clinical trials (trial A: n = 37, trial B: n = 48). Refractive error and axial length data were obtained at 6-month intervals using cycloplegic autorefraction and partial coherence interferometry, respectively. Progression rates for right eyes were defined for the first and second 6 months of the studies and classified in terms of "summer," "autumn," "winter," or "spring" based on the mid-point of the 6-month period between visits.', 'The mean 6-month spherical equivalent progression was -0.31 ± 0.25 D for summer, -0.40 ± 0.27 D for autumn, -0.53 ± 0.29 D for winter, and -0.42 ± 0.20 D for spring (p < 0.001). Mean axial elongation was 0.17 ± 0.10 mm for summer, 0.24 ± 0.09 mm for autumn, 0.24 ± 0.09 mm for winter, and 0.15 ± 0.08 mm for spring (p < 0.001). Post hoc analysis indicated that data for summer and winter were different from each other at p < 0.05 for both myopia progression and axial elongation after adjusting for age.'] Is myopia progression in Chinese children slower in summer than in winter?