Solid phase enzyme-immunoassay (EIA) was employed to assess the antigenic reactivity of matrix protein (M) and nucleoprotein (NP) of influenza A virus adsorbed to polystyrene in the presence of different detergents such as beta-octaglucoside (OG), Triton X-100, Tween-20, sodium dodecylsulphate (SDS), sodium deoxycholate (Doch-Na), Nonidet P-40 (NP-40), and sarcosyl at concentrations ranging from 0 to 2%. The antigenic reactivity of NP was the highest in the absence of detergents. For M protein, Doch-Na, SDS, NP-40 and sarcosyl of 0.05-0.1% enhanced the chromatophoric response in EIA 1.5-2 times. In contrast, the antigenic reactivity of M protein remained unchanged after OG or Triton X-100 treatments, and it decreased in the presence of Tween-20.