Three different phosphate buffered saline extracts of Litomosoides carini were prepared and examined by gel diffusion, immunoelectrophoresis and disc polyacrylamide gel electrophoresis using sera from infected cotton rats and antisera from hyperimmunized rabbits. Using disc polyacrylamide gel electrophoresis, up to 22 protein, 6 lipoprotein and 4 glycoprotein bands were identified. A minimum of 8 precipitin lines were detected by gel diffusion and a maximum of 11 precipitin arcs by immunoelectrophoresis when pooled rabbit antiserum was used. Using infected cotton rat sera, fewer number of precipitin lines and arcs were detected. Two precipitin arcs did not have a counterpart on examination against pooled rabbit antiserum. The importance of these two specific antigenic components for use in immunodiagnosis of human filariasis has been discussed.