Summary Rapid treatment of influenza virus directly on the microscope grid with non-ionic detergent has allowed better visualization of the internal component. Many micrographs show that this ribonucleoprotein (RNP) is present as a continuous strand of 6 nm diam. arranged in the form of a double coil or helix. In spite of the minimal treatment to which the virus was subjected most helices still showed signs of degradation. The findings that we have obtained lead us to suggest that the RNP component of influenza virus must be very sensitive to both chemical and physical manipulations, any of which could cause it to fracture from one continuous strand into several pieces, although such breakages could possibly occur at specific points along its length.