The filarial nematodes Wuchereria bancrofti, Brugia malayi and Onchocerca volvulus represent major public health problems in the Tropics. Effective diagnosis of infection with these parasites is required both for administration of drugs to infected individuals and for monitoring of control programs. However parasitological diagnosis is associated with a number of problems including frequently inadequate sensitivity, long pre-patency of infection and inconvenience for patients. For these reasons there has been considerable effort expended in developing other forms of diagnosis, in particular immunoassays for measuring antibody and circulating parasite antigen as well as molecular-biology-based assays for detecting parasite DNA. This article reviews the progress and achievements obtained to date. The latter include the development of ELISAs employing recombinant antigen for detection of antibody to O. volvulus which have both high sensitivity and specificity, the commercial availability of immunoassays to measure circulating antigen in W. bancrofti infection and the generation of specific DNA-based detection systems for all three parasites.