The epidemiology of Lyme borreliosis (LB) in Tayside was studied and compared with Highland (an area of high endemicity) and the rest of Scotland. From April 2001 to March 2008 the incidence of LB in Tayside rose from an estimated 2.57 to 5.84 per 100,000 population. In 2008/09 the incidence of LB in Tayside increased further to an estimated 13.85 per 100,000 population. This rise was significant and, although numerically less than that in Highland (37.24 to 49.69 per 100,000 population), it was proportionally much larger (137% vs 33%) and confirmed that LB in Tayside has diverged from that in non-endemic Scottish regions. The dramatic rise of LB in Tayside cannot be accounted for by changes in laboratory protocol or changes in the number or demographics of patients tested. However, changes in climatic conditions and alterations in clinical presentations may have contributed to this significant rise.