Studies were undertaken to monitor for the presence of Borrelia burgdorferi, the etiologic agent of Lyme disease, on Prince Edward Island, Canada. Gut contents were removed for culturing from seven engorged ticks collected in 1991-1992 including five Ixodes dammini (Spielman, Clifford, Piesman & Corwin) and two I. scapularis (Say) removed from a dog that had recently traveled to the southern United States. B. burgdorferi was recovered from one I. dammini that had been removed from a cat in Charlottetown in October 1991. The cat had not traveled off the island. Immunofluorescent antibody (IFA) studies on sera from 75 dogs, 7 cats, and 8 white-tailed deer (Odocoileus virginianus) collected on Prince Edward Island between 1989 and 1992 revealed one reactor with an IFA titer > or = 1:256. The reactor was a dog with a history of travel to the United States. This report documents the first isolate of B. burgdorferi in Atlantic Canada, possibly because of the introduction of I. dammini on migratory birds. Serological studies do not indicate widespread occurrence of B. burgdorferi on Prince Edward Island.