Conditions of the enzyme immunoassay for the detection of HSV-I by the "sandwich"-method at all stages of the testing were optimized using monoclonal antibodies (monoAB). When identical concentrations of monoclonal antibodies and durations of their adsorption on polystyrene plates were used, the signal in EIA (A405) with carbonate buffer was by 30% higher than that for PBS. A similar increase in the signal was observed at a temperature of incubation of 37 degrees C as compared with that at 4 degrees C. Even during 18-hour incubation at 37 degrees C no inactivation of monoAB occurred. It was further shown that saturation of the surface of wells with protein was achieved at a concentration of monoAB 5-10 micrograms/ml, and under these conditions the optimal dilution of the conjugate was that corresponding to antibody concentration of 1.5 micrograms/ml. When ABDC peroxidase and 5-aminosalycilic acid were used as the substrate, the presence of HSV-I was regularly detected even with a concentrated virus preparation diluted 500-1000-fold (corresponding to approximately 5.0 1g TCID50).