During recent years many seroepidemiological studies have been published about Lyme borreliosis in various European countries. This paper presents a review of these studies to clarify the geographical incidence of the infection by B. burgdorferi in Europe and particularly in Italy. Data of Lyme disease seroprevalence has been established in European patients or at-risk populations and in blood donors or control subjects. In Northern Europe the sero-prevalence of antibodies to B. burgdorferi in patients or in at-risk subjects is higher in Sweden, 19% and lower in Estonia, 2.7%. In Central Europe the incidence of antibodies to B. burgdorferi in patients or in at-risk subjects is higher in The Netherlands, 28% and Switzerland, about 26%, and lower in Poland, 15%. The range of antibodies to B. burgdorferi in blood donors or control subjects shows the highest spikes in Ireland 15% and the lowest in Austria 7.7% and in Germany 5.5%. In Southern Europe we have the highest incidence in Croatia, 43%, while we have the lowest incidence in Greece, 1.1%. In Italy the seroprevalence of antibodies to B. burgdorferi in patients or in at-risk subjects seems to vary, in Northern Italy, from the lowest incidence in Lombardia 3.2% to the highest in Friuli 22.3%; in Central Italy, from the lowest incidence in Emilia (Parma) 0.2% to the highest in Toscana 18.3%. The range of antibodies to B. burgdorferi in blood donors or control subjects shows the lowest spikes in Lazio 1.5%, while the highest are in Sicilia 10.9%. Although the amount of works on infection diffusion by B. burgdorferi is increasing, the statistical evaluations, comparisons and the drawing of acceptable conclusions continue to be difficult. In fact data, obtained from various European laboratories, are often not directly comparable, because of different serological tests used to detect antibodies to B. burgdorferi. Consequently it seems very important the work that could be performed by a multicenter study on the standardization of the criteria to be used in WB interpretation, presently in progress among several different European laboratories, and the necessary consequent efforts to elaborate a common panel of criteria about the comparison of the data.