Objective: The LRR (leucine rich proteoglycans) is a molecular recognition motif found in proteins with some roles in cell adhesion, signal transduction, DNA repair and RNA processing. OPTICIN is a member of this family. Takanosu et al (2001) detected messenger RNA expression of mouse OPTICIN in the eye, heart, brain, testis, thyroid and epididymis by dot blot hybridization. In this study, expression levels of mRNA and protein of OPTICIN was investigated by two monoclonal antibodies which were raised against OPTICIN peptides. By this method structure of OPTICIN in human and mouse has been studied. Materials and Methods: Mouse tissues including, kidney, testis, liver, lung, heart, brain, muscle, spleen and eye were isolated. OPTICIN expression was identified at mRNA and protein levels by RT-PCR and Western blot. Results: PCR analysis revealed that OPTICIN mRNA is expressed in all the tissues studied except for the lung. However, OPTICIN protein was detected in all tissues analyzed. Conclusion: Expression of OPTICIN in the adult murine tissues may suggest functions other than that of putative regulation of vitreous collagen fibrillogenesis for this molecule.