Lyme Borreliosis is an infectious disease caused by the Borrelia burgdorferi spirochete transmitted to man by a tick bite. The aim of this study was to assess the predictive value of tick bites for the diagnosis of Borreliosis in a sample of 266 subjects residing in an endemic area of north-eastern Italy. In the serological diagnosis of Borreliosis, positive and negative predictive values of tick bites were found to be 24% and 88% respectively.