A test system based on EIA was developed for evaluating the efficiency of drugs active towards the respiratory syncytial virus (RSV) in cell culture. Virasole and its structural analog ribamedii active towards RSV infection and arbidol whose activity in RSV infection is unknown were tested. Like virasole and ribamedil, arbidol inhibited the expression of RSV antigens, the inhibitory effect increasing with the drug concentration and decreased with increase of the multiplicity of virus infection. MIC50 for arbidol, virasole, and ribamedil were 10, 5, and 6 micrograms/ml, respectively. These data prompt clinical trials of arbidol in RSV infection.