The incidence of tick-borne encephalitis (TBE) has more than doubled in Switzerland in recent years. In the French part of Switzerland several patients seem to have acquired the infection outside of known endemic foci. Thirty patients with TBE living or having acquired the infection in the French speaking part of Switzerland between 2000 and 2005 were identified. For one patient it wasn't possible to obtain precise information about the place of acquisition of the infection and 16 patients were infected in known endemic foci. Among the 13 remaining patients, 6 were infected on the southern shores of the lake of Neuchâtel and 7 in the plaine of Orbe. We conclude that there are new foci of TBE in the northern regions of the canton of Vaud. Vaccination should be proposed to the population at risk of these regions. In addition it is important that persons with outdoor activities in this regions respect the preventive