Lyme disease is very common in the countries of the northern hemisphere. In Italy it is endemic in some regions of the northern part of the country and it is more frequent during summer. In Calabria (south Italy) no cases have been reported. To document the presence and indigenous nature of Lyme disease in this territory we conducted a study from 1999 to 2002. We defined as indigenous cases those with erythema migrans with the following characteristics: dimensions equal to or greater than 5 cm; localization on an area of the skin where there was a tick bite; appearance between 4 and 30 days after the tick bite; appearance in patients who had not resided out of Calabria in the previous 3 months. We found 23 patients with the necessary characteristics to be defined indigenous cases. Since 15 of these cases (65.2%) were observed in the October - December trimester and no case was found in the July - September trimester, we suspect that in Calabria the disease follows a seasonal distribution which differs with respect to countries where it is historically endemic.