In 14 patients with Lyme disease skin biopsies, synovial specimens and a lymphnode showed lymphohistiocytic infiltrates, often perivascular. Obliterative alterations of blood vessels and fibrinoid were characteristic for infection of synovium. Spirochetes were demonstrated in all specimens by the Bosma-Steiner silver impregnation method. Spirochetes were localized in dermal papilles and subepidermal zones of skin sections of ECMA, in lymph vessels and collagen fibres. In synovia of patients with arthritis the spirochetes were found beneath the synovial lining cells and perivascularly. In the lymphnode of a patient with arthritis and lymphadenitis the spirochetes were localized in and round the blood vessels and in the lymph vessels.