Epoxyeicosatrienoic acid (EpETrE; EET) metabolites of arachidonic acid such as 11(12)-EET and 14(15)-EET have been identified as endothelium derived hyperpolarizing factors with vasodilator activity. Soluble epoxide hydrolase (sEH) catalyzes the conversion of EETs to the corresponding dihydroxy eicosatrienoic acids (DiHETrEs; DHETs) thereby diminishing their activity. CUDA is an inhibitor of sEH exhibiting IC50 values of 11.1 nM and 112 nM for the mouse and human enzymes, respectively. In COS-7 cells, 10 µM CUDA blocks conversion of 1 µM 14,15-EET to 14,15-DHET by 94%. CUDA activates peroxisome proliferator-activated receptor α (PPARα) 8-fold at a concentration of 10 µM but exhibits no affect on PPAR.delta. or PPARγ.