Background: The aim of this study was to describe and categorize the different predominant patterns of PCR confirmed erythema migrans (EM) and to study possible correlations according to the clinical pictures and Borrelia substrains. Methods: Patients over 18 years old, seeking care with tick exposure and an EM were consecutively included during a study period of three years. We evaluated clinical and laboratory findings with regard to Borrelia burgdorferi s.l. spirochetes detected with nested Osp A PCR in skin biopsy specimens. Laboratory and serology testing were done acute, after 6 weeks and after 6 months. The patients were clinically evaluated at the initial visit and repeatedly after 14 days unitl recovery. Results: 118 patients (women=54, men=64) with a positive B. Burgdorferi s.l. PCR analysis were included. In this area totally 73.7% of the EM were caused by B. afzelii and 26.3% by B. garinii (p=0.0001). Leisons caused by B. garinii had a shorter duration from tick bite to the initial visit (p= 0.001) but there were no differences between the sizes of the EM, indicating a faster development of lesions caused by B. garinii. Patients with lesions caused by B. garinii to a greater extent had presented with fever at the initial visit (p=0.02). Also patients with B. garinii lesions to a greater extent had elevated levels of CRP at the initial visit (p=0.006). 45% of the EM were categorized as “annular”, 27% as “homogeneous”, 19% as “central erythemas” and 9% as “atypical”. The lesions caused by B. afzelii were predominately “annular” and the lesions caused by B. gaarinii were predominately “homogeneous”. Conclusions: In this study most EM were caused by B. afzelii. Leisons caused by B. garinii developed faster and the patients to a greater extent presented with fever and elevated levels of CRP at the initial visit. Leisons caused by B. garinii were mostly homogenous and by B. afzelii were mostly annular.