Endogenous trefoil (TFF) peptides have reparative and anti-inflammatory actions in colitis because luminal application in vivo potently reduces inflammatory indices and accelerates healing. Since chronic production of NO via inducible nitric oxide synthase activity (iNOS) leads to tissue damage and inflammation, we tested whether TFF2 could inhibit NO production in a monocyte cell line in response to bacterial endotoxin, and in vivo by measuring inflammatory indices and nitrated protein expression in rat colon after colitis induction. We showed that TFF2 can inhibit iNOS and NO in monocytes and inflammatory compartment size in vivo, and conclude that trefoils can regulate monocyte NO-mediated inflammation in colitis.