Four cases of [apparently infectious] erythema chronicum migrans occurred within a 1-mo. period in SE Connecticut [USA]. The syndrome may include advancing erythematous rash stemming from an apparent insect bite, hyperesthesias, myalgias, malaise, fever, lymphadenopathy, and, rarely, meningitis. Treatment with penicillin, the tetracyclines or erythromycin usually results in prompt resolution.