Identification of Rickettsia isolated from Dermacentor marginatus ticks from Portugal.Using recently developed techniques (shell-vial isolation, PCR/RFLP genetical methods, SDS-PAGE), serological studies and animal induced pathology to isolate and characterize tick-borne rickettsiae.A total of 632 adults D. marginatus ticks were captured. From the collected ticks, we isolated 18 Rickettsia strains and the results confirm that the isolates from the haemolymph were identical to R. slovaca reference strain.Dermacentor marginatus ticks infected with Rickettsia slovaca were found in Portugal. This occurrence extended the known, geographical area for this microorganism. It is also a factor that could alter the seroprevalence rates of butonneuse fever. The pathogenicity of this Rickettsia should be evaluated to determine its responsibility for diseases other than butonneuse fever.