Abstract. Thrombosis, sometimes with infarction, occurred in 20 of 52 dogs with renal amyloidosis. Pulmonary thrombosis was most commonly encountered, although the heart, kidneys, intestine, and other tissues were occasionally affected. Recent thrombi and older, organized thrombi occurred, sometimes in the same animal. The possible role of dehydration, hemoconcentration, hyperfibrinogeneniia, hyperglobulinemia, and clot-promoting factors in producing a hypercoagulable state is discussed.