Onchocerciasis and lymphatic filariasis (LF) are major causes of severe morbidity and considerable socio-economic problems throughout the tropics. Vector control and mass chemotherapy have helped to control these infections in some regions, but the temporary success of such measures argues strongly for the development of vaccines. Success in such a venture will require detailed knowledge of protective immune responses in conjunction with the identification of target antigens. By comparison with other important parasitic infections, such as schistosomiasis and leishmaniasis, work on the development of vaccines for onchocerciasis and LF has been constrained because of the difficulties of producing cyclical and patent filarial infection in laboratory mice. Wolfgang Hoffmann and colleagues here outline the opportunities presented by the rodent filaria Litomosoides sigmodontis for filarial research.