AIM:To investigate the retinoic acid receptor-β(RAR-β) expression in guinea pig eyes and study the relationship between the RAR-β expression and experimental myopia. ·METHODS:Fifty guinea pigs were randomized into the normal control group(n=10),defocusⅠgroup(n=20) and defocusⅡgroup(n=20). Guinea pigs in the defocus groups wore-10.00D lenses on the right eyes:defocusⅠgroup,wore lens for 14 days,and defocusⅡ group for 28 days. The left eyes didn’t wear lenses as self-control eyes. The refraction and axial length were measured before and after wearing lenses respectively. The protein expression of RAR-β in retina was detected by immunohistochemisty and Western blot. RT-PCR was used to observed the level of RAR-β mRNA in retina. ·RESULTS:Compared with the control eyes,the lens-worn eyes of defocusⅠand Ⅱgroups became myopic and elongated(P<0.05,respectively),and the degree of myopia was lower and axial length was shorter in groupⅠthan those of groupⅡ(P<0.05). The protein expression and the mRNA level of RAR-β in retina of the defocus groups increased significantly (P<0.05),while decreased significantly in choroid and sclera(P<0.05). ·CONCLUSION:Expression of RAR-β in guinea pig may play a role in the lens induced myopia.