In Europe, various species of ticks can be infected with several different pathogenic microorganisms, e.g., Borrelia burgdorferi (see Chap. 5), tick-borne encephalitis virus, and Rickettsia conorii. Prerequisite for proper management of a tick bite is the awareness of whether the tick in question stems from an area that is endemic for any or several infectious agents. For instance, in an area endemic for borreliae and tick-borne encephalitis virus, the patient might need passive immunization against the tick-borne encephalitis virus, unless he or she is protected by active immunization; measurements to counteract a possible borrelial infection may also be necessary. The following Chapter will solely be concerned with tick bites in areas which are endemic for the B. burgdorferi infection (see Chap. 29).