Spirochaetes were demonstrated in material from patients with Lyme disease by short-time high-concentrate silver impregnation after treatment with amylase. Removal of mucoid material was essential to visualise Borrelia burgdorferi. Lyme spirochaetes were demonstrated in material from 23 patients with Lyme disease--erythema chronicum migrans (ECM) 10, lymphadenosis benigna cutis (LABC) 7, arthritis 4 and Bannwarth's syndrome 2. Spirochaetes were localised in the subepidermal zone, peri- and intravascularly, and in collagen fibres in ECM and LABC, and beneath the synovial lining cells in arthritis, producing marked vascular changes with fibrosis and synovial hyperplasia. Spirochaetes were also demonstrated in CSF from a patient with Bannwarth's syndrome.