The cuticle of the filaria Dipetalonema viteae was isolated by sonication in 1% sodiumdodecylsulphate (SDS) and in a mixture of 1% SDS and 5% B-mercaptoethanol (BME). Sonication in SDS removed all internal parts and left the cuticle intact; this was verified by light- and electronmicroscopy. Sonication and incubation of the cuticle in the mixture of SDS-BME at pH 6.8 dissolved the basal and part of the median zone of the cuticle. The epicuticle and the cortical zone remained intact. The extracts were investigated using SDS-polyacrylamide gel electrophoresis; the early extracts contained a wide variety of proteins, whereas the later steps showed a consistent pattern with a smaller number of bands. Cuticles after SDS-purification, the extract of cuticular material in SDS-BME, and the cuticles insoluble in SDS-BME were used to immunize mice; the antibodies produced were visualized by an indirect fluorescent antibody test on cryostat sections of female worms. When SDS-purified cuticles were used for immunization, antibodies directed against all organs in the filariae were found. The SDS-BME extract and the insoluble cuticular pellet stimulated the production of antibodies restricted to the cuticle of adult worms and microfilariae. The purification method opens up the possibility of further isolation and characterization of antigens from the cuticle.