A 45-year-old man presented with circumscribed scleroderma (CS) on the extremities. Histology of lesional skin showed the typical manifestations of scleroderma including a perivascular and interstitial infiltrate of lymphocytes and plasma cells; in one of the biopsies spirochaetes could be detected. Despite treatment with penicillin, progression of CS was observed and spirochaetes were isolated from skin cultures obtained from active scleroderma lesions. These spirochaetes were identified as Borrelia afzelii by sodium dodecyl sulphate-polyacrylamide gel electrophoresis of outer surface proteins and polymerase chain reaction (PCR) analysis of their chromosome. After two courses with ceftriaxone the lesions stopped expanding and sclerosis of the skin was diminished. At this time cultures for spirochaetes and PCR of lesional skin for Borrelia afzelii DNA remained negative. The pathogenetic role of Borrelia afzelii in the development of CS is discussed.