Inhibition of cyclooxygenase (Cox) enzymatic activity by non-steroidal anti-inflammatory drugs (NSAIDs) provides the molecular basis of analgesia following wounding or surgery. This study investigated the role of Cox activity in the regulation of vascular endothelial growth factor (VEGF) expression in keratinocytes and the formation of new blood vessels in acute wounds in mice. To this end, human HaCaT keratinocytes were stimulated with epidermal growth factor (EGF). EGF increased Cox-1 mRNA in the presence of the constitutively expressed Cox-1 protein in keratinocytes. EGF coinduced Cox-2 and VEGF mRNA and protein expression and an accumulation of prostaglandin E (PGE ) in cell culture supernatants. Inhibition of Cox isozyme activity by Cox-1 and -2 siRNA or ibuprofen reduced PGE and VEGF release from keratinocytes. In a mouse model of excisional wound healing, Cox-2 and VEGF expression were colocalized in the granulation tissue of acute wounds. Oral treatment of mice with the Cox-1 and -2 inhibitor diclofenac was associated with reduced levels of VEGF protein and an impaired blood vessel formation in acute wound tissue. In summary, our data suggest that a reduction of PGE -triggered VEGF protein expression in wound keratinocytes is likely to contribute to the observed impairment of wound neovascularisation upon Cox inhibition.