To report the myopia progression (change in axial length) of a boy in whom the progression was slower in the eye treated with overnight orthokeratology (ortho-k) than in the fellow eye with no visual correction. An 11-year-old boy was fitted with an ortho-k lens in his left eye in 1999 in a private practice. The refractive errors were OD -0.25 - 0.75 x 168 and OS -2.50 - 0.50 x 170 before commencing ortho-k lens wear. He participated in one of our research studies and made yearly visits to our clinic in 2001, 2002, and 2003. Logarithm of the minimum angle of resolution (logMAR) visual acuity, refraction, ocular health, and axial length were assessed at each visit. At the visit in 2003, the unaided visual acuity was OD 0.40 logMAR and OS -0.04 logMAR. Between 2001 and 2003, there was a small increase in axial length in the left eye (0.13 mm) but a significant increase in the axial length (0.34 mm) with a corresponding increase in spherical equivalent refractive error (0.75 D) in the right eye. This case suggests that myopia progression may have been slowed down by ortho-k lens wear in the eye undergoing treatment of a boy undergoing unilateral ortho-k treatment.