Retinal ischemia promotes retinal neovascularization. Vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) are important growth factors for neovascularization. We did experimental retinal vein occlusion (RVO) and examined the expression of basic FGF and FGF receptor 1(one of the basic FGF receptors) by in situ hybridization. We used adult pigmented rats (Brown-Norway strain). Dye laser photocoagulation (577 nm) was applied to the retinal arteries and veins within two disc diameters of the optic nerve head to injure the retinal vessels. After one week, laser photocoagulation was applied to only the retinal veins to occlude them (RVO model). As a control, laser photocoagulation was applied to the posterior retina avoiding the retinal vessels. After treatment, the eyes were removed and 10 microns thick cryostat-cut chorioretinal section were used for in situ hybridization with probes as mentioned above. In the RVO model, expression of messenger RNA of basic FGF (b-FGF) and FGF receptor 1 increased in the inner nuclear layer and the inner segment of the photoreceptors, and appeared in the retinal vessel wall in the early stage. This shows that b-FGF and FGF receptor 1 increased in the ischemic retina, and were produced on the retinal vessel wall. This suggests that b-FGF may be involved in protection, regeneration, and proliferation of the retinal vascular endothelial cells in retinal circulatory disturbance.