Recombinant filarial proteins are of interest as potentially protective immunogens for lymphatic filariasis. We have previously identified paramyosin, myosin, and a heat shock protein 70 (HSP) 70 as prominent immunogens in individuals residing in an area endemic for lymphatic filariasis. Our goal in the present work was to identify the Brugia malayi tissues that contain these proteins. Polyclonal rabbit antisera with high levels of immunoglobulins to each of these proteins were prepared for use in indirect immunofluorescence microscopy studies of third-and fourth-stage larvae (L3's and L4's) and adult worms. Myosin and paramyosin were found within the longitudinal somatic musculature in all of these life stages. In L4's and adult worms, myosin and paramyosin were also detected within the walls of the reproductive and alimentary tracts of male and female worms. HSP 70 was evident within the somatic musculature, hypodermis, lateral chords, alimentary tract, and reproductive structures in L4's and adult worms. HSP 70 was not detected in sections of freshly obtained L3's. However, L3's cultured at 37 C for 24 hr before fixation demonstrated a classic heat shock response. In these larvae, intracellular HSP 70 was observed in all tissues. None of the antigens studied appeared to be located on cuticular surfaces.