The effects of lymph stasis on thehistological and biochemical properties of thecoronary arterial wall and on the coronarycirculation were studied in 72 dogs. Cardiaclymph stasis was produced in 52 dogs bycardiac lymphatic blockade whereas in 20 dogsonly a sham operation was performed. Blockade of cardiac lymph drainage promotedcharacteristic injury to the coronary arteriesincluding subendothelial edema with plasmaimbibition, interstitial and intracellular edemain the tunica media with degeneration in thesmooth muscle layer, swelling of the adventitialspace with dilated lymph vessels and, later, fibrosis. The biochemical properties of thecoronary arterial wall also were adverselyaffected by cardiac lymph stasis. Thus, thecollagen and hexosamine content of thecoronary arteries increased and the metabolismof the coronary wall shifted in an anaerobicdirection. Whereas coronary blood flow wasslightly decreased with lymph blockade, thecoronary circulatory reserve capacity and theadaptability of the coronary vascular systemwas markedly reduced. The histologicalchanges were most apparent in the smallercoronary arteries. The coronary microvasculaturewas also pathologically altered with thedevelopment of numerous coronaryarteriovenous microshunts. These findings inconjunction with other experimental andclinical information suggest that impairedcardiac lymph drainage contributes to thepathogenesis and progression of coronaryartery disease.