The internally situated influenza virus structural antigens (matrix and nucleoprotein) and the glycoprotein hemagglutinin were assayed using rocket immunoelectrophoresis or single radial diffusion following disruption of purified virus with 1% w/v sodium sarcosyl detergent. Electrophoresis was carried out for 1-4 h in 0.05 M barbitone buffer at pH 8.6. The potency estimations of HA and M activity were similar for the two methods for bivalent beta-propiolactone inactivated whole virus vaccines.