Surface plaque matrix (PQM) and a tubular arrangement of filaments border Trachipleistophora hominis parasites during growth within host muscle. The PQM at the parasite surface forms a network of processes which can be associated with filamentous tubules. Peroxidase tracer delineated the PQM and showed apparent connections with the tubules. The tubules at the interface of T. hominis-infected cells are structurally similar to the extrasporular tubules of the microsporidian, Ameson michaelis. The extrasporular tubules of A. michaelis and the proteins from T. hominis-infected muscle reacted to keratin antibodies, K8.13, K4 and K13. Conversely, antibodies produced to T. hominis-infected muscle, reacted with the extrasporular tubular proteins of A. michaelis. The PQM and tubular elements are thought to play an important role in affecting molecular traffic between the host and parasite.