Clinical symptoms were studied in 161 consecutive patients with erythema chronicum migrans Afzelius and in a follow-up study signs of late manifestations were investigated. General symptoms such as headache, fever, myalgia and/or arthralgia were found in about half of the patients with a disease duration of less than or equal to 3 weeks. Three patients had coexisting lymphadenosis benigna cutis. Two untreated patients developed meningitis/meningoradiculitis and one untreated patient arthritis. The importance of a sufficient antibiotic therapy to prevent late manifestations is stressed. Although there are many similarities between erythema chronicum migrans Afzelius and Lyme disease, the results of the present study also point to differences. Multiple skin lesions, pronounced general symptoms, laboratory abnormalities and major symptoms from the joints were less common in patients with erythema chronicum migrans Afzelius than reported in patients with Lyme disease, but a prolonged course of the skin eruption was more common.