Lyme disease is a tick-borne multisystemic Borrelia infection to which the following diseases belong: erythema migrans, lymphadenosis benigna cutis, lymphocytic meningoradiculitis (Bannwarth's syndrome), Lyme-arthritis and acrodermitis chronica atrophicans. The infection rate of ticks with Borrelia Burgdorferi in Germany amounts to 13.6% compared to the infection with the European spring summer meningoencephalitis virus with 1.1%. Recent investigations show that lipopolysaccharides and interleukin-1 play an important role in the pathogenesis of Lyme disease. Lipopolysaccharides (LPS) are a constitutive part of the outer wall of gram negative bacteria. Its biological activities include pyrogenicity, mitogenicity for lymphocytes and the induction of interleukin-1 (IL-1). IL-1 is the major macrophage-derived immunoregulatory protein. Lyme disease is characterized by a variety of symptoms which could be explained by the effects of IL-1 on host systems. These symptoms include: fever, malaise, erythema migrans and arthritis. The clinical course can be divided into three stages. Erythema migrans, lymphadenosis benigna cutis and general symptoms characterize the first stage. In the second stage disorders of the heart and the neurological system may follow including Bannwarth's syndrome. 60% of the patients develop facial palsy and 30% of these patients bilateral palsy. In 40% of all cases the facial palsy is the only motor disorder. Other cranial nerves can also be affected. The third stage consists of the Lyme-arthritis, acrodermitis chronica atrophicans and encephalomyelitis. The determination of specific spirochetal antibodies in serum and cerebrospinal fluid (CSF) is the most valuable diagnostic aid for this borreliosis. The CSF examination may also be helpful.(ABSTRACT TRUNCATED AT 250 WORDS)