Nymphal Ixodes ricinus ticks collected from woodland areas in South Wales, UK, were tested using the polymerase chain reaction for the presence both of the causative agent of human granulocytic ehrlichiosis (HGE) and Borrelia burgdorferi. Twenty-two of 60 (37%) ticks were found positive in the PCR for B. burgdorferi and 4/60 (7%) for the HGE agent. One tick was found positive both for B. burgdorferi and HGE agent. Our findings imply the presence of the HGE agent in UK ticks and the finding of a tick apparently containing both pathogens underlines the potential for concurrent infection with HGE agent and B. burgdorferi to occur after a single tick-bite. Based on our observations, we conclude that there may be a need to consider a range of pathogens both in laboratory investigation and clinical management of suspected tick-borne disease in the UK, particularly where there is a clinical presentation atypical of Lyme borreliosis alone.