Aims: Epoxyeicosatrienoic acids (EETs) are vasoactive and angiogenic lipid mediators produced by cytochrome P450 arachidonic acid epoxygenases and chiefly metabolized by the soluble epoxide hydrolase (sEH). The aim of this project is to determine the role of the CYP/sEH pathway in the regulation of vascularisation in the retina. Methods: Retinal vascularisation in sEH^-/- mice and their wild-type (WT) littermates was studied during at postnatal (p) days 2, 5, 7 and 9 using immunofluorescence and confocal laser scanning microscopy. Results: Retinal vascularization was markedly delayed in sEH^-/- mice at p2 and p5 (sEH^-/- /WT vasculature area ratio: 32.6%, P<0.001 and 60.5%, p=0.001, respectively). Vessel density and pericyte coverage were significant lower in the sEH^-/- pups at p9. A similar effect at p5 was induced in WT pups treated with an sEH inhibitor (sEH/Sol. vasculature area ratio: 71.8%, P=0.01). While in the systemic circulation the sEH is expressed in endothelial cells, this was not the case in the retina. Rather that sEH was expressed in capillary pericytes as well as in Müller cells and the end-feet of astrocytes. Interestingly, the EET-generating enzyme Cyp2c44 also demonstrated a similar localization in mouse retina. Moreover, a high level of sEH was expressed in primary cultures of murine Müller cells. Conclusion: Taken together these data indicate that the CYP/sEH cascade is required for normal retinal vascularisation, and that a product of the sEH is involved in glia-vascular coupling in the retina.