The main purpose of this study is to determine whether four weeks treatment with oral doxycycline is as equally effective as three weeks treatment with intravenous ceftriaxone in patients with Lyme neuroborreliosis. The other purpose is to improve laboratory diagnostics of Lyme neuroborreliosis and further define the manifestations and epidemiology of the disease in Finland.

Inclusion Criteria for definite Lyme neuroborreliosis (Criteria 1-3 or 1 and 4 fulfilled):

1. Neurological symptoms suggestive of LNB without other obvious reasons
2. CSF pleocytosis (>4 leukocytes per mikrol)
3. Intrathecal production of B. burgdorferi specific antibodies
4. Detection of B. burgdorferi DNA in central spinal fluid

Inclusion Cirteria for possible LNB (criteria 1 and 2 or 3 fullfilled):

1. Neurological symptoms suggestive of LNB wihtout other obvious reasons
2. Production of B. burgdorferi spesific antibodies in serum
3. Erythema migrans during the previous three months

Exclusion Criteria:

• pregnancy and breastfeeding
• women planning to get pregnant in two months
• age under 18
• handicapped persons
• prisoners
• use of any antibiotics two weeks before study treatments begins
• allergy for tetracyclines or cephalosporins