We examined jun-B gene expression in the rat retina after a focal retinal injury by in situ hybridization. 30 min after producing a penetrating retinal wound, the retina showed the expression of jun-B mRNA intensively in the inner nuclear layer (INL) and relatively sparsely in the ganglion cell layer. The double-labeled retina by immunocytochemistry and in situ hybridization demonstrated that jun-B mRNA within the INL surrounded S-100 protein immunoreactive cytoplasm in the middle sublayer of the INL. These results suggest that the jun-B expression is induced mainly in Müller cells following retinal damage.