It is now known that erythema migrans disease (as described by AfzeIius and Herxheimer'), acrodermatitis chronica atrophicans,* lymphocytoma of Bafver~ tedt,~ meningopolyneuritis (Garin-Bujadoux-Bannwarth~ yndrome):~ and Lyme disease (as described by Steere in North America) 6s7 are all one and the same disease caused by B. burgdorferi.* All of these disorders are histopathologically characterized by variable infiltrates of perivascular lymphocytes and plasma cells, and vascular damage and fibrin deposits in the synovia of arthritis patient^.^ Primarily cutaneous and neural in involvement, the disease has come to be understood as a multisystemic infectious syndrome involving the cardiovascular system, central and peripheral nervous system, and reticuloendothelial and gastrointestinal systems."*" Involvement of these and specialized systems produces clinical symptoms that can correlate with varying degrees of tissue damage caused by a complex interplay of cells of the immune system and humoral factors such as interleukin-1 (IL-1), circulating immune complexes, prostaglandins, collagenases, and possibly compounds derived from arachidonic Experience in both hemispheres now points to ever-expanding clinical and pathologic lesions that heretofore have been referred to by a variety of seemingly unrelated terms. Many of these involve the skin in chronic phases. Increasing evidence points to the continuing presence of spirochetes in these lesions. This paper summarizes these alterations as seen histopathologically.