In Norway, physicians and patients alike are becoming increasingly aware of Lyme borreliosis. This fact has created a need for information on different aspects of this disease. This paper reviews the historical background for Lyme borreliosis and the epidemiological situation in Norway, based on data collected by the national system for notification of infectious diseases (MSIS) in 1993. The role of the tick vector and the overall clinical picture is presented briefly. The authors discuss indications for and possibilities of different microbiological diagnostic methods, and finally list the recommendations for treatment and prophylaxis.