Abstract.From 2 senior‐high and 2 vocational schools in Taipei, 3251 children with age 16–19 were randomly selected to study the relationship between ocular refraction and its main optical components, corneal curvature and axial length. While the corneal curvature was found to play only a minor role in the determination of ocular refraction, the measurements of axial length parallelled the degree of myopia (r = 0.74). A two‐years' longitudinal study of additional 411 children from one junior‐high school (age 13 through 15) further pointed to the importance of axial length in the production and progression of