An association between infection and Tourette's syndrome (TS) has been described repeatedly. A role for streptococcal infection (PANDAS) has been established for several years, but the involvement of other infectious agents such as Borrelia Burgdorferi or Mycoplasma pneumoniae has only been described in single case reports. We examined antibody titers against M. pneumoniae and various types of antibodies by immunoblot in patients and in a sex- and age-matched comparison group. Participants comprised 29 TS patients and 29 controls. Antibody titers against M. pneumoniae were determined by microparticle agglutination (MAG) assay and confirmed by immunoblot. Elevated titers were found in significantly more TS patients than controls (17 vs. 1). Additionally, the number of IgA positive patients was significantly higher in the TS group than in the control group (9 vs. 1). A higher proportion of increased serum titers and especially of IgA antibodies suggests a role for M. pneumoniae in a subgroup of patients with TS and supports the finding of case reports implicating an acute or chronic infection with M. pneumoniae as one etiological agent for tics. An autoimmune reaction, however, has to be taken into account. In predisposed persons, infection with various agents including M. pneumoniae should be considered as at least an aggravating factor in TS.