The ability of three common tick species from Georgia to maintain and transmit the causative agent of Lyme disease, Borrelia burgdorferi, was compared under laboratory conditions. A B. burgdorferi cotton rat isolate (MI-6) from Florida was selected as a strain from the south, and the SH2-82 isolate from New York was used as a positive control. Amblyomma americanum (L.) and Dermacentor variabilis (Say) did not transmit the MI-6 isolate from inoculated hamsters to naive laboratory mice, and nymphal ticks did not maintain this isolate transstadially. Ixodes scapularis Say transmitted both isolates to laboratory mice. There was a significant difference in the percentage of transmission of the two isolates. I. scapularis also transmitted the MI-6 isolate to two of three cotton rats. This study adds support to the premise that I. scapularis is probably the main tick vector of B. burgdorferi in the southeastern United States.